I'm not a serious dice collector, but here's one idea --
At the annual CCA chip show in Las Vegas a few weeks ago, there were dealers in attendance selling dice.

The booklet for the chip show is available online at the link below.
It lists dealers, the kinds of collectibles they were selling, and their contact info. You might try contacting some of the ones that list dice.

See page 38+ for their names & info:
https://ccgtcc.com/documents/1346/2024-Casino-Chip-and-Collectibles-Show-Program

Good luck.