First you may try Dallas North Aquarium, or a LFS and see if they have any in their tanks, I picked 3 of them at DNA this Tues for .25 each. Also Jo Ann Fabric, Hobby Lobby, and Michaels Crafts carry shells. If you purchase these make sure they are not covered with clear paint. Also if you purchase these shells be sure to boil them in RO/DI water for 10 minutes to clean them, allow them to cool before throwing in the tank. Hope this helps.