About 15 years ago I sold 5 and 6mm straight wall trillion bezel
models to Boston Gems and Findings in Boston. 1-800-225-2436. At that
time they were unavailable. I assume they still make them, if not, I
still have molds on them. Frei & Borel now sells a trillion bezel
block if you want to make your own sizes of tapered bezels.
Gold and Platinumsmithing