Gibson made the SG Pro for 2 years, and the pickup and rings are a different size than a traditional P90, so they are literally unobtianium at this point. I acquired my 72 SG Pro and the brittle bakelite pickup rings were cracked (at best) and destroyed. I found one guy in who was selling his original bakelite rings for $300+ for the pair (my guess is they would have never survived the shipping). I took the original that was still in tact and taped it back together to get dimensions and start trying to figure out if it would be a viable replacement for the original covers. It worked out great, and if these ever break, I can always just make some more, or in different colors if I want to upset the vintage purists.
This is such a specific design and build that it really should be available to people who will never be able to get their hands on these rings again. Enjoy!
I hope this helps.
The author marked this model as their own original creation.