For you in the States, the AKA is attempting a comeback. For a long time, they gave up distributing fish, their reason to exist. They went with Aquabid, a good online auction source. I hear they have their own networks again.
On Aquabid, European sellers can't ship to the US legally. The border stops everything fishwise without expensive bureaucracy. The inside the US sellers have nice fish, but have jacked their prices very very high. And honestly, at this time of year with the cold, I would not buy from a hobbyist breeder. It's Russian Roulette season.
Storewise, there are a limited number of species imported, from of all places, the Czech Republic. The really colourful Aphyosemions lay a couple of eggs a day and don't grow super fast. A tetra drops hundreds of eggs that are ready for market in 3 months. Raising killies needs a new tank every week for most species, and you get 10 here, 20 there... they'll never appeal to commercial producers.
The Czechs cottage breeders produce a couple of Fundulopanchax, Aphyosemion australe and sometimes Chromaphyosemion bivittatum or biteniatum, though rarely. If you go that route, breed them fast as the fish aren't always the healthiest. One that can easily live 3 years might last a year after its travel and treatment in pet stores.
But It's November. I only buy in person from October until April. Now is exactly when we want new projects, and when it's most hazardous to fish to be shipped.