Drats! Sorry I should have read further back. The only person I know who could have spares is Bill Benton (if you haven't already tried).
No problem! I'm still working on Mr. Bill to source some for me out of his mystical CB750 cave.......or spend $500 on a benchtop lathe and try to make my own.
Here's some pics of my restored gauges. I did the ole paint-can-opener-pry-trick to bend back the backside of the chrome retaining ring. Of which I was able to reuse once it put them back together. The black cover was blasted and powdercoated, new faces from our site sponsor CB750faces.com (excellent product), needle tips painted, and chrome back plates got a quick buff.
I thought this was kind of cool, the old plate faded except where the needle rested above. To me that meant the bike sat outside and weathered the elements for a decade or two.
now to put em on the bike............