I did some calculations to find the dimensions of the C4 bomb in CS (using the terrorist's pinky fingernail as a refrence of 1cm).
In CS, the bomb is about 6.7cm(3") tall (JUST the c4. that is, minus the keypad / LCD screen on top), 12.5cm(6") wide, and 23cm(9") long. Since it's not very practical to try and pull it off in such a small volume, I doubled these measurements to get something to work off of.
Goal for dimensions: 13.4cm(6") tall, 25cm(12") wide, and 46cm(18") long. I went looking on Newegg hoping to get lucky and find a MicroATX case with something similar to these dimensions, but they all seem to run too long or short in one dimension. This, however, could be solved by constructing an addition to one end of the case (lengthwise would probably be easiest).
I'm going to go see what I can come up with for a mock-up. If any of you guys know of a case (plain would be best) that would come pretty close to these dimensions, please let me know!