For escargots, Decent sized cold storage should have it. I got mine from Vivocity. Located under frozen section. A dozen for about $15.
Alternatives would be turbo shells for hermit crabs. c328 has them.
Not the best shells for shellies but if you have aggression issues, can consider fox conch shells for scaping or breaking line of sight. JXZ has 2 similar types there or you can PM Johannes.
Last but not least, 1/2 inch plastic pipes. Easily available at most hardware stores. Ease of maintenance and hurling of fries . Idea stolen from
http://youtu.be/ofivFER_RvQ
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