Buying foam as mentioned above would be the best route, as well as buying vinyl in the same manner, then laying the vinyl over the foam and bolting it between two pieces of 2x2 or 2x4 surrounding the area on all sides. You don't just want to wrestle on the foam alone. Unless you actually want to get ringworm, staph, etc... as it would be fairly close to impossible to get anything other than the top of the foam clean and everything will get absorbed into it.