what about taking a piece of scrap metal 1/8'' or so thin in the size you want it, drill a hole through it, stick a tee nut through the hole, and maybe jb weld the base of the tee nut to the metal? just my though to save even a little more coin for something you wont see after its turfed over.
That's basically what I did except I found that it was cheaper to buy clinch nuts instead of T nuts and JB weld.