I've been trying to find cases to display my figures in, but there was only one or two on evilbay. I would think that someone would have mass produced them by now..
I have some DID display case, they're "dust proof" and you can put a couple of figures per case if you want. The only problems that I have with them is the take up room and after you put your figures in them you can't mess around with them unless you unscrew the top.