On this parts fiche the Cotter Valve is the most specified component.
The most reasonably priced component used on the Gsx250es 1982 (z) General Export (e01) Cam Shaft - Valve is the Bolt(6x12.5).
The Gsx250es 1982 (z) General Export (e01) Cam Shaft - Valve consists of twenty-eight pieces with the Cam Shaft, Exhaust being the most expensive.