After market angle finder M ???
I seem to remember a Japanese company offering screw-in angle finders and diopters for Leica M but I can't find the site anymore. I do remember that due to a licensing issue, they could only sell them under the pretense that they were for SLR cameras (Leica apparently patented the idea of an angle finder for a rangefinder camera - which is like patenting the use of chocolate sauce on chocolate ice-cream).
Anyone know what I'm talking about and where I can find these guys (again)?