The most reasonably priced component used on the Sfx50mm 1999 (x) Switzerland Rear Wheel (2) is the Dust-seal, Brake.
In this schematic the "Spring Brake Shoe" is used most often.
A sample from the products for the Rear Wheel (2) include: Cam,rr.brake, Spg,rr.brake Arm, Nut,u,16mm, Nut,adjust.