Wouldn't you know, I ended up in a cigar shop yesterday. Bought a Helix cigar in its metal tube (looked about right). It fits the epi pen perfectly in diameter (without the plastic) and has enough room for some foam in the ends as cushion. It also still fits in my spec-op case as well. While it has a cork seal on it, I think I will put a wrap or two of teflon tape on the threads.

By the way, anyone want a cigar, I don't smoke.