I don't see any reason you could not replace the bracket with a new one from Scamp
if your wheel would go on it (or the old one if they have it, as Jon said). It would be a bit of a project, removing some of the liner, drilling new hole(s) and maybe sealing up old ones. It would also give you a chance to inspect the wood reinforcement that the bolts go through (and that the plate sits on) to see if water has intruded and caused any rot.
Edit: for the new bracket, Scamp
Must have rim with 5 x 4 1/2" bolt pattern. Works only on rims with 5 lug nuts. Rims with 4 lugs nuts not compatable.
(Yes they misspelled compatible on the website
I removed my spare and carry it in the tug. That has a number of advantages so maybe you can do that. I had considered removing the bracket and bolts since its so ugly now with no spare on the back, not to mention people think I am nuts for towing cross-country with no spare for the trailer (which I do not do of course). But I decided to leave it in place.
Edit #2: It just occurred to me that the bracket
looks like something they likely build in-house (does anyone know?). If so it should be easy for them to make one up for the older (or any) wheel.