They appear on eBay very occasionally. You need to search in all countries because the majority of odds and ends are in Germany.
There are different rings for different lenses because of the differing lengths of the barrel. Harry Fleenor in California still has them but they are expensive. I bought one from him to complete my set.
For the shortest barrel lenses (80mm and 50mm) you can improvise by sticking a small piece of material (rubber, plastic, metal) to the part of the lens that rotates with the aperture ring. It has to be in the right spot. The piece of material is placed so that when the lens is mounted and is set on full aperture it moves the prong on the camera just a bit. Once it moves a little the meter can be activated. Closing the aperture moves the prong further. The prong on the camera is spring loaded so that it will follow the little block on the lens as the aperture is opened.
I will do some measurements and take some pictures, but I'm in a hurry now but tomorrow i'll post more details.
Last edited by john_s; 09-11-2011 at 05:49 PM. Click to view previous post history.