There are people on this forum who sell shrimp (for sale section!) or even many breeders who sell home-bred shrimp.
Be sure you get a buffering substrate that lowers the pH (ADA, SL-Aqua, Prodibio, Controsoil.... would not recommend Fluval), RO water (RO unit, or buying from a store) and GH+ minerals. You'll need liquid GH and KH test kits, if you don't have them already plus a TDS meter. If the TDS meter doesn't come with a calibration solution, be sure you get that as well from the same company as the TDS meter.