I agree with Markus, I found thes. You can find these relays in salvage yards, bought the entire used relay, just for bushings. You will find these in several MB models 1965-1980.
Robert Hyatt
Williamsburg, VA.
1970 280SL, Red on Silver,4-speed, Euro spec; 1999 C230 Kompresser Sport, Black on Black; 1990 Miata, Black on Red, 5 Speed