I occasionally find surplus military transit cases that often would accomodate just about anything you could find film for. The Army uses them for all kinds of stuf, and are often waterproof. You'll find a lot for night vision goggles, which are too small, but I've seen them for field computers, rocket launchers, Satcoms, etc. that would proably be large enough.
Now if I can just get my 20x24 built.