easy enough to make one out of wood. I did it for a cross country move a couple years ago with a 2x4 skeleton, a bunch of sheets of 7/16" OSB, and about 300 screws. Wood sealant or paint on the wood and seal up the seams with silicone and it's water tight. It was cheap when I did it, but with wood prices now it's probably double what I paid to do it