I had 2 pairs of them several years back. I put them on the swap area and they went fast. They are not straight plates. They have a slight twist to them. Good luck finding a pair. If you can't find any, I think you could make some that would work using the correct nuts soldered or welded to a small metal plate for each screw location. Put some JB Weld on the plate and then tighten the screws with the stanchions off, making sure the screws line up with the stanchion countersunk holes. Once the JB Weld is cured, you should be able to remove the screws and install the stanchions. The nuts can hardly be seen inside the bottom of the stanchions.
Rusty Nelson