where to find shrimp cull?

just want some cheap shrimps to add to my tank. I saw some online for 15 rupees each but they're out of stock :,) i have a 3 gal tank that's lying around with some potting soil and sand that I'm going to fill up with water and put my water lettuce in. would be nice to add some shrimps to it also never kept shrimps before but im not new to aquariums