Once again I find myself in a confusing situation. Due to some bad choices and luck my tables wizard almost lost his spellbook.

Short on cash, he came to me with an idea. One I need help with.

The cost of the scribing includes the ink, just so you're aware. It represents the cost of the unusual and special inks you need.

You could use Fabricate to make ink, I suppose but you will have to homebrew the costs of the raw materials (because they will need to match the scribe cost). It's also not easy to answer what you will need because inks can be made from a variety of sources. Basic inks are just dyes, such as from plants, in water. More expensive and higher quality inks are made from many ingredients treated through multiple chemical processes and those would, arguably, be too complicated for Fabricate. You'd probably need proficiency with Alchemy too.

All in all it'd be far easier to find a way to give them the coin to get those inks, and just scribe normally. Wizards have a variety of ways to use their magic to make money in non-adventuring ways.

For instance a Transmuter with woodcarving can use their Minor Alchemy to turn metal into wood, then use woodcarving for making fancy dolls or idols or engrave intricate markings and then let it turn back to metal - or even fashion keys and such more easily - take a big piece of metal, turn to wood, chop off what you need and fashion it how you want, let it return to metal.

Continual Flame is an awesome for-business spell. Sure, it's 50 gold each time but an everlasting and safe torch? People would easily pay 100 gp or more to have these in their home.

You can ritually cast Alarm an infinite number of times so you can try selling this as a service in an inn - go to one of the fancy inns and there's no doubt that they would pay for the alarm to keep them safe.

Water Breathing is great to open a diving school. A whole day where you can dive deep and never worry about drowning? It's a no-cost ritual, so go to some beach and make money.

Fabricate when you have proficiency with things like carpenter's tools or smith's tools or such as can let you produce items for sale in a fraction of the time and with almost no effort and since you can pretty much get materials from nature easily, like wood, there's not even a cost to you. With some creativity this is arguably the most profitable spell that you can repeatedly use without consequence.

Creation can let you make anything you need like gems to sell. Sure they'll disappear eventually but by that time you'll be gone and with the coin and if you use Disguise Self or something you don't have to worry about getting caught later. Ah, and for those that look out for such things, hide the magic with Nystul's Magic Aura (aka Arcanist's Magic Aura). Or create the tools or stuff you need for making things, which goes well with fabricate.

Demiplane can be sold as long term storage solution if you can get people to trust you.

Unseen Servant and Tiny Servant are great way to sell some nifty services for cooking, cleaning, fetching, carrying and more.

Wish I am not talking about the just wishing for gold because that carries risk of never being able to cast it again. Just the spell replication basic use is fine because hey, you can give somebody immortality. Clone basically lets a person jump to a new version of their own bodies that can be younger so basically they have a failsafe even if they would normally die from old age, they instead don't die and just end up in a younger version of their own body. Normally this is very expensive and you need a piece of their flesh and it takes a long time to cast. But with wish you ignore all of that and just like that, in an instant, there is a container with a piece of their flesh in magically appearing and in 120 days time they become safe from death, at least once. Can you imagine how much people would pay for that? You can also use Wish to make an instant Simulacrum and they will have all your level 1 to 8 spell slots and know all your spells etc. Basically, double the creation, fabricate, etc for more profits in half the time.

There are many, many, ways a Wizard can make profits even without adventuring or making scrolls with services even the lowest commoner would want and  can pay for. So it should not be difficult for your Wizard friend to make the gold needed for the inks/scribing. Then they can just scribe a new book or save time with Fabricate and calligraphy proficiency. This will be much easier than trying to homebrew a way to fabricate the high quality inks which would definitely require alchemy proficiency.

Why not just give him the ink and supplies he needs? Spends a few days asking around, and yes there is a supplier of such rare things down by the harbour. Don't have enough money for what you need? Ah well there is this task I need taken care of quietly... and so on. No need for bending the rules of magic, or forcing the poor wizard to sell his magic like some common street conjuror.

Or have him pawn a magic item to get the money.  Then there can be a race to get enough money together to buy it back before it gets sold.  And then an adventure to find and barter/steal from new owner if he misses the deadline.  Or he can just borrow money from other party members and pay them back later.  The rogue may want interest on his loan.

Especially since you said he lost it through bad choices, I might just make him wait until he's earned some money to make a new one.  Having to rely on cantrips for a while can be a remarkable teacher. 

I would rule; a spellbook requires a high degree of craftsmanship and therefore fabricate is a bust. don't lose your spellbook!

No, I disagree.  You CAN make complex items if you can craft them with your tool proficiencies.  For a future person asking the same question:

To make the pages:
1) he needs paper, or plant fibres to convert to paper or papyrus
2) he needs leatherworking proficiency and animal hides (for Parchment)

To make the bindings and cover:
1) leatherworking for a leatherbound journal
2) woodworking or carpenter's proficiency for a simple wooden cover (ref 1)

For ink:
1) alchemy
2) herbalism
3) a few squids (which I guess can also be skinned for a kind of leather?)

All this will allow the fabrication of a new book if he cant find one to purchase.  The issue comes with the spells.  This is covered in the wizards spellcasting ability itself under replacing a book:
"You need spend only 1 hour and 10 gp for each level of the copied spell." Time can probably be ignored with fabricate
"If you lose your spellbook, you can use the same procedure (listed above) to transcribe the spells that you have prepared into a new spellbook. Filling out the remainder of your spellbook requires you to find new spells to do so, as normal. For this reason, many wizards keep backup spellbooks in a safe place."

He can thus fabricate a new book in 10 minutes with his spell for the cost of 1 blank book (or the materials and skills to make one) and 10gp of ink per spell lvl per spell he has memorized at this time.  This can be reduced to 5gp per spell level if he posesses alchemy or herbalism proficiency (as he could fabricate the ink from base components at standard 1/2 cost).  He has to rebuild his spellbook from scratch with spells he doesnt have currently prepared in the usual, expensive manner, or from gaining future lvls.  Always keep a spare up to date book!  Or... order of scribes wizard who can summon the book's spirit to a new book complete with all it's spells... or maybe be a L3 pact of the tome warlock multiclass and use the pact book as your spellbook, as you're patron will scold you and give you a replacement after an apology ritual!

(ref 1) https://i.pinimg.com/564x/83/2e/70/832e7069a73dd927ce2ded4e92d17aef.jpg

Why does he not have enough down time to just make a copy without the spell?

My characters always make back up books. The problem is finding good places to hide them.

I do not know if you forgot but the components should be V,S, and M. Because of the description alone.

There are five kinds of spellbook in my current setting. Not all are books, lol.

I also don’t like the “only the rich have spell books” thinking, because poor people can be wizards too. So there should be a simple way to create a spellbook — one that takes time and effort and energy, and would be something taught to them by a master at the earliest levels of study of their craft.

spellbooks may be made fancier over the years, more involved, more costly, but not to start.

in my game, losing a spell book is reason to go to war. Because spells have to be found or bought or bartered. So that loss would be devastating, and worth going after it at all costs.