Does anyone reproduce these? Or, what vendor might sell these?

Won't be OEM, but they wouldn't be difficult to produce something that would work and look nearly correct.
I believe I would make one of those in 3 pieces, a washer on the bottom, a spacer that makes up the difference between the bottom and the top piece, and the square outer piece with the hole drilled through, all welded from the bottom side. Gene

AMD should make those. They may be on the floor pan, though and available separately.