Cheaper Pontiac Arm Rest Suggestions

Best matierials to build a cooler in the arm rest of my car?
I am interested in building a can cool in my
1998 Pontiac grand Prix GTP
arm-rest. it cna fit about 7 or 8 can with a small storage spot at the bottom for some sort of cooling device. But i am worried about to much moisture building up and molding
and also .. i cant think of any matierial to keep it cool
Any suggestions