I am in need of one of the plates that fits under the mounting bolt on a Simplex SLJ and many other simplex derailleurs. It is teardrop shaped, about 2.4cm long, and has a tab bent at 90-degrees that rests against the hanger stop. There might be two small holes drilled in it, but I can drill those if not. This part was common to many '70s and '80s Simplex RDs. So if you have a trashed derailleur with one of these plates, I will gladly buy it, or just buy the plate.
You can see one in this photo on the right-hand side under the black allen-head bolt: http://www.speedbicycles.ch/
Thanks,
Chris
http://velo-orange.blogspot.com/
Chris Kulczycki
Velo Orange
109 Colonial Avenue
Annapolis, MD 21401