I've seen them at many shops. They aren't generally found in chain stores, but I wouldn't say they are hard to come by at the locally owned shops.
If you can't find any good local shops, try finding an aquarium club. A lot of times, members will sell fish to you, or at least point you in the right direction toward quality shops.
I am curious about the price range of these guys. Cuz down here i was lucky to get 2 of them for $4 each. They got really colorful after a few days in their new and nicer environment so i decided to get 4 to 6 more of them. Only to find that they were at $10 now... is that the averege prize elsewhere?