Parts such as the Cylinder (tc125a: Spark Plug, Stud 8x25, Cap,spark Plug, Gasket,cylinder Head (mca) are included in the Tc125 1977 (b) Usa (e03) Cylinder (tc125a parts fiche.
On this parts fiche the Pad,cylinder is the most specified component.
The Nut (8mm) is the lowest priced item on this Cylinder (tc125a schematic.