Off the top of my head, I can think of over 15 different stores in the St. Louis area that sell retro games...a few that have more uncommon stuff, and one that has a good selection of imported games. As for thrift stores around here, there are a bunch of those as well. They are pretty hit and miss as you would expect, but it's where I've found probably 80% of my collection and generally at a really good deal.