Linens N things
Try Linens N Things in the bath department, also other stores like that. The stick on fish coordinate with a set with shower curtain, towels, and so on. Maybe even Walmart bath dept.
Also try a wall paper store, there are wall paper borders that have fish on them, you can ask for a sample and get a 1 foot section, might have 2 fish on it. Walmart may have wallpaper with the bath stuff if it coordinates.
Most of these will be sort of large, 2 to 4 inch fish, and mostly saltwater type fish.