Pushrod,
I'm sure someone does, but then you have to ask, whether or not you want holes in your truck for the required snaps?
On my previously owned 52, the prior owner made his own. It covered up the "shot" bedwood very nicely. To Boot, it was fairly cheap to make.
He built a frame (bed height) with an upright in each corner. Then he placed a sheet of plywood on top of the frame. Covered that, glueing some 1/4 (or so) foam on top, then covered the foam with vinyl.
The whole unit sat in the bed of the truck, covering up the ugly bed, yet was easily removed, if and when I wanted to haul anything.
I think I may have some pictures around, if it would be of any interest to you. There's one small one kinda showing what I'm talking about at the bottom of the gallery page.
http://www.stovebolt.com/gallery/coulter_eric_1952.htm