Not that I usually shop there for fish, but Meijer (I think you have them in NY) always have synos. They are labeled there as lace cats. They ship small though so no idea how they will hold up in your tank.
I suspect your best bet is to have a good look at the synos generally available. Loads of pics etc here. Then you'll know what you're looking at in the shops. Prices vary greatly from species to species. Multipunctatious and Petricolas, when you find them, are usually not cheap whereas Eupterus are easily available and cost somewhat less. Many recommend the first two mentioned for Cichlids from lake Malawi but I've found any synos (with the exception of the Angelicus) will happily be compatable. I only leave out that species as if you have one that's all you can have. They are the bullies of the syno world, and stress out other synos and their own species too. They will live with other catfish types happily enough, so long as they're smaller.
Hugs,
P.
Dwarf petricola would be a good choice, if you could afford a group of them. Three at least anyway. Lovely looking and come out in the daytime. They aren't as nocturnal as many of the syno breeds. Finding them could be tricky but I'd suggest trying a browse of internet sites for good stores in your area that do the less common syno breeds. If you were in the UK I could point you towards some without hesitation but being in America I really can't help.
Other species suitable would be nigriventis, multipunctatious (both in groups) Alberti (although a very shy species even with company and wouldn't recommend alone)....actually almost all species would be happy but how many depends on the breed and their adult size. Look through the planet catfish link in my last post and see what appeals then go from there.
Hugs,
P.