Retaining Ring

Hello, Fellow APUGers,

I just purchased on E-Bay a 150mm Rodagon enlarging lens. The deal did not include, unfortunately, a retaining ring. The thread size looks to be about 50mm, verified by trying a 49mm ring(too small) and a 52mm ring(too large). When I tried my favorite St. Louis camera store earlier today, I struck out completely. Does anyone know where to find the appropriate ring for this lens?

Konical

I bought one from Midwest Camera over the phone for my 150 mm Rodagon. www.mpex.com ,I think.

lee\c

I am in a similar position. I plan to buy one from the B&H used department. Some are just $5.

Rich