Improved familiars

I started D&D back in the 70's with the blue box Basic D&D.  From there AD&D and so forth.  IIRC, back in those editions there was a spell (no feats back in those days) that allowed a Wizard to get get an improved familiar like a Psuedo-dragon and such.  I want to say it was around a 3rd level spell or higher.  

With 5e or 5.5e is there a way for a Wizard to get an improved familiar?  Something beyond taking a 3 level dip into Warlock to get the Pact of the Chain.  Something Wizard specific?  From what I am seeing RAW/RAI there is not a way.  However, I don't claim to know every thing there is to know about 5e and 5.5e and may have missed something?  If there is a resource I'd like to know what that resource is so that I can take a look.

Beyond that, I'm guessing if there isn't a resource then it would be a homebrew.  Has anyone gone this route?  Did you make it a feat?  A spell?  Class feature?  All ideas welcome and thank you. :)

Generally, in 5E if you want to have a psuedodragon, imp, or the like as a familiar and you're not a Pact of the Chain warlock you'd need to find or summon the creature in question and then convince it to become your familiar via negotiations.  Which is of course contingent on the GM's allowing it.

Very recently a book called Arcana Unleashed was published which includes a bunch of feats that improve familiars, as well a new spell called Battle Familiar that creates a more powerful familiar; that might be worth looking into.

The strixhaven book has some options for more interesting familiars tied to your house. 

Thank you.  I now have some new things to look into :)