You could always get a small utility trailer. Harbor Freight has some small collapsible ones for about $200. DOT approved and about 4x8 (the size of a standard sheet of plywood). You would just have to buy a 3/4" sheet of PT ply for the flooring. It will only hold about 900-1000 lbs, but can be handy. I have one, but when it is empty, tends to bounce around.