For small shells, I recommend wood cases; then the shells would be kept
in those litle plastic boxes. That's the way I do it with my Epitoniums.
I don't currently have the address, but Horatio Buck makes cabinets. He
calls them "Buck Boards". I believe he monitors this web page. The thing
about wood is that you can specify the dimentions (height, depth, width.
My Ep cabinet has six 2" drawers, six 3" drawers, and one 5" drawer at
the bottom. I made it my very own self in a high school woodshop---on my
period which was supposed to be devoted to making lesson plans and
grading papers.
        Art