In this schematic the "Stopper,cushion" is used most often.
The most reasonably priced component used on the Cb550 Super Sport 550 Four Cb550f2 1977 Usa Rear Shock Absorber(1) is the Bolt Hex 10x32.
Some items from this specific schematic: Nut,hex.,10mm, Seat,under Spring, Adjuster, Spring, Washer 10mm.