Do they sell fish at the pet store?

They most definitely cell fish at a pet store why would you think otherwise. You can easily buy an aquarium of various sizes. I think you would be able to answer your question rather better, you should go and check out the pet store and see what you get there. If you get fish that would be great don’t you think so? You would have to go there and ask them if they sell fish, probably you could ask them where you could get the fish from. Normally every pet store has fishes for sale too. It is not very difficult to find fish. See if you could find a complete fish store otherwise. There are pet shops which do not sell any other animals but fishes. It would probably be by the name aquarium or something related to fishes. Good luck.