I'm trying to give the Sorcerer at my table something to regain during short rests as he's the only PC that doesn't benefit. My plan is that they'll regain sorcery points up to their proficiency bonus. 

I've tried doing this with a homebrew magic item based on the Shards in Tasha's and with the Metamagic Adept feat, but can't get it to work.  Any ideas? 

I don't want to give them additional sorcery points (as the metamagic adept feat does), but they restore the points they already have.  I want it to work automatically when they take a short rest so less book keeping for the player. 

Tasha's Cauldron actually added the Bloodwell Vial which does this, though it's also an attuned arcane focus that boosts spellcasting, which you may not want? It is however available in +1 (uncommon), +2 (rare) and +3 (very rare) varieties so may be a good item to consider giving your player?

I'm a bit unclear what you mean in terms of not getting your item to "work" though? There's no way to automatically give back sorcery points on the character sheet, it's just a described effect; in the case of the Bloodwell Vial it just tells you how many sorcery points you get back (5 in its case) and has a single charge that you can use to mark off when you've used that ability, since it can only be used once per day. The player has to add the sorcery points back themselves though, as they might when using Font of Magic.

Update: Whoops, I keep using [spell] tags when I don't mean a spell. Thanks IamSposta!

That tooltip that went wonko is a bloodwell vial.

Theres really nothing you can do to actually affect the sorcery points themselves as that’s a base class feature. You would just need to put a single charge on the item and write it in the description and the player would tick of the charge and untuck the boxes. The system was originally designed as a digital representation of a pencil and paper, so you mark the box and erase the marks in the other boxes, but with a click or tap. It isn’t video game automated, it gust a pretty digital version of a paper sheet with some stuff appearing integratedish, but it doesn’t actually “do” anything. It just looks like it should.

Thanks for the help both. I did look at bloodwell vial as an option as I'd hoped the sorcery point recharge on a short rest would have been coded in when that item came out. 

I'll add it as a feat and give it to the PC next session so he's got a reminder he can do it, and will tell the player out of game he'll have to do it manually. 

Dndbeyond finally made short rests be a bit more automated so thought this could be possible. 

Hi! Though you worked out how to do what you're wanting to do, I'd like to make a comment on this plan. You probably already know this, but the Sorcerer level 20 feature is to regain 4 expended sorcery points when you finish a short rest. So having your player's sorcerer regain up to their proficiency bonus renders this feature moot. This also gives an indication of how special sorcery points are considered to be. And though the Bloodwell Vial may allow them to regain 5 points after a short rest, that's only once a day.

And honestly? It's not a bad thing to have one character not get an extra benefit from a short rest, since it means they can actually do stuff while the others are resting, like investigating the scene for loot after the battle is over. This is doubly true for Rogues, who also don't get a short-rest extra benefit until level 20, and tend to be good at Investigation. And Wizards get their Arcane Recovery just once per day, so similar deal during other rests. All these classes are going to tend to stay out of the thick of battle, so they often don't need a short rest to regain hp. 

You can do what you want as a DM so that you and all your players are having fun, it's just something to keep in mind.

Quote from bonnkansan >>

It's not a bad thing to have one character not get an extra benefit from a short rest, since it means they can actually do stuff while the others are resting, like investigating the scene for loot after the battle is over. 

 
That’s true. But I find it advantageous for such characters to have a limited short rest benefit. If  they have something that says:

“Whenever you take a short rest you can… …You can use this ability once, and regain the use of this ability whenever you finish a long rest.”

Then, when they don’t net to spend Hit Dice but the rest of the party does, and there is nothing else to do, then their PC is not sitting around twiddling their thumbs while waiting for the others to finish their naps. And with the recommended two to three short rests per day, if they don’t need to use it they could save it for the next rest, or if they used it already then they could also still investigate or whatever on subsequent rests. Having an option is handy, IMO it’s mostly when everyone has reasons to spam rests that it’s an actual problem. 

A wizard with arcane recovery can cast a maximum 29 spells without factoring other features. Arcane Recovery being used to regain 4 1st levels and 3 2nd levels for maximum castings.

A sorcerer with Sorc Points can cast 32 spells by using their points to make more 1st level slots. 

They don't need arcane recovery. They technically have more spellcasting resources than most classes and can use it more flexibly since it takes bonus actions instead of 1 short rest per day. That's why they dont have arcane recovery: they dont need it.

The sorcerer capstone where you regain 4 sorc points on a short rest is generally regarded as one of the worst capstones in the game, and it wouldn't even make it not worth anything, it'd just add to the amount you get. I considered allowing a sorcerer to spend a hit dice to regain sorcery points. 

Comparing arcane recovery and sorcerery created spells is a bit of a weird point too, since sorcery points are often not actually used for creating spell slots.

Yeah, but you know converting Sorcery points to spell slots is the least efficient use of their Sorcery points. The Wiz and arcane recovery by itself is not an even comparison. A more even comparison would be:

A Sorcerer (no subclass) without any Metamagic at all converting all of those Spell Points to Spell Slots; and 10 additional known spells, 1 at every odd level

Vs.

A Wiz (no subclass) with Arcane Recovery, but no Ritual Casting; no Spellbook (so know ability to learn additional spells and no ability to prepare spells); a Class Spell List 1/3 it’s current size; only the 6 + 2/level spells they automatically learn, and no Spell Mastery.

Compared that way then I might agree with you. But to just compare it as you did without all the rest is giving too much value to the Point-Slot conversion and ignoring everything else a Wiz has going on.

If a Sorcerer got a version of Sorcerous Restoration at 2nd level that scaled at the same pace as Rage, and an additional Metamagic at 3rd (or something equivalent), and Spell Mastery, and a better capstone… then it would be on par with the Wiz IMO.

Sure, regaining your proficiency bonus of sorcery points after a short rest once a day isn't going to break anything, especially if the player is feeling left out.