OP, no they do not sell these type speciality fish at Pet Smart or Co. The OP needs suggestions for fish he can purchase at Pet Smart or PetCo. 2 platy's, 2 swords, 6 neons, 1 dwarf blue gourami, and 4 Panda or Julii Cory's will work fine. I have a couple 20g tanks and this is not over stocked. You said you already had the 2 platy's and swords so you have to work with what you already have. Go to the Pet Smart and PetCo, see what they have, make a list of what you like, come home and research each fish. Look at adult size, minimum size tank needed, are they good communtiy fish not aggressive. Then make an educated decision of what you would like. Ask for stocking levels after you pick the fish you like/want. But don't do fancy goldfish. One needs a 20g by itself, they get very large, and need very good filtration, and large weekly WC's. I have 8 6+ inch fancy goldfish and their tank care is very demanding.