Buy a roll of 3-4 inch foam rubber and cut it to fit. Then just roll it up and take with you...I am getting a shell for my truck and I am thinking about camping out of it when warm weather arrives. I have the five foot bed but I am fairly short so I should be ok. I am however having a hard time finding an air mattress that is short enough to fit with the tailgate closed. They do not seem to come in a five foot length. I did find one designed for a truck bed but it is over $200 which, imho, is too much for an air mattress. Anyone have any ideas?