I had the same thought so I oredered one and and it came today however, it's made from brittle plastic. It's fine for display but would not hold up well.
If you interested I ordered the one for the Military Challenge Coin (2" or 50mm) #Y65.
Scroll to the bottom of the page.
http://www.air-tites.com/Air-Tite_Ring_Type_Coin_Holders_1.htmGreat company to deal with by the way <img src="/ubbthreads/images/graemlins/thumbup.gif" alt="" />