Want to Buy WTB: Series VIII adapter ring for 12" Commercial Ektar

The 12" Commercial Ektar has an unusual front thread, and no commonly available filters will fit. According to the 1953 Kodak Ektar Lens Catalog at cameraeccentric there's a special ring that adapts this lens for use with Series VIII filters. I'm not sure if the ring came with the lens or was a separately-purchased item, but none came with my 12" CE.

I know SKG can make one for me, or I could con a machinist friend into doing it, but finding a proper ring might be easier (or not, time will tell).

How about a step up ring that is a close fit over the front. A thin layer of foam or felt to fill the gap.. (It is something I've used on oddball lenses in the past).