My goto custom gaffed card maker has decided to retire. I'm looking for anyone else who might be in the same business. I know about the large companies making full decks but my need is more for on-demand small sets of cards (e.g., Three Card Monte gaffs). Any leads would be appreciated.

Tracy at House of Chuckles should be able to help you.

https://www.houseofchuckles.com/

Cannot beat http://www.martinismagic.com/

I'll second martinismagic.com. I bought an acrobatic card from them 15 years ago that finally gave up the ghost. I asked Marty how much for a replacement, and he refused to sell me one, insisted on sending me a replacement (which I just received today, which is why I'm on the Gaffed Card forum tonight). That's a rare and beautiful thing in this day and age...

Without question or concerns, call Marty! A gentleman, a pro and is the Best.