Just get a high quality piece of tupperware, not the new disposable stuff, and a new sponge (the inexpensive, plan old sponge, not a fancy kind) and a jug of distilled water.

Saturate the sponge and put it in the microwave on high for 2 mins or so. (until it's almost dry) and it should be sanitized if not sterilized. Then add more distilled water and squeeze it until no water comes out and put it in the tupperware. Add cigars and enjoy.