Honda Rav4 Spare Tire Mount
I saw a guy use the spare tire mount off of an older Rav4 (where it is bolted to the rear door) on the bed. Same bolt pattern. Not sure if the newer ones would work, though, they probably will not be "plentiful" at the junk yard.
The final product will look like a full-size spare lying flat on the bed, but not sliding around. Pretty nifty.
I just got one, and I will be doing that on mine soon. I won't get to it for a while, but once done, I will post pictures.