I found couple, on instructables I think, and quite frankly, they sucked. Really nothing more than a shadow box or ---smurfy--- picture frame with a bit of felt.
Anyhow, I did design one out of acrylic that was a combination shadow box and shelf but dropped the project when I discovered what happened to the minty fresh boxes and manuals I tried to keep for the better part of twenty years. Apparently, keeping them in a nice box deep in the back of the closet doesn't actually equate to the idea that you don't want anything happening to them. I call it the mom curse. Damn thing runs in the family according to my father (born in 1921... think about that).