Here's an idea, either go to your LFS and ask for shells, or go to the craft store, get a bunch, and boil them out. :yes:
FWIW, you can buy dry goods without issue. The shells, unfortunately, are listed as livestock and there you need the minimum. The shipping and handling on those (packing costs) are pretty high and time consuming to afford it for much less.
Perhaps you can nicely write SWF and ask if the shells could be shipped as dry goods? But it is easier to go to the craft store, and requires a lot less emotional input.