How about just using an 8x10 picture frame, turn it upside down, and put the guts in backwards or use one of the leftover 8x10 cardboards, like the ones that Ilford puts into their paper packages, as a backing. Then drop in the paper, then neg, then glass on top. To get it apart, just slide the frame off of the easle and push everything out from the bottom.

Should be pretty simple and cheap or free depending on how well stocked you are on frames.