I always wanted one, but I never did buy one. Too expensive for my high school student budget. Of course, I could use my programmable calculator to generate random numbers as well, so...
This past weekend, I was at the Dollar Store and I saw this:
You can put a set of dice in there just fine. There's plenty of room to shake them around.
You can see the dice very easily through the clear bottom of the container. I plan to make one with 7d20 (of different colors) in it to rapidly generate "to hit" and "saving throws" for multiple monsters at once -- or to roll multiple attacks at once.
I'll let you know how it turns out!