On this parts fiche the Washer Oil Bolt is the most specified component.
Some items from this specific schematic: Screw-washer,4x12, Clamper,master Cy, O-ring,14.8x2.4, Bolt,flange 6x14.
The lowest price component in this Rear Brake Master Cylinder (2) parts-list fiche is the Screw-washer,4x12.