On this parts fiche the Nut,flange,10mm is the most specified component.
The Washer Seal, 6mm is the cheapest item from this partsfiche.
Parts such as the Cylinder Head: Bolt,flange,6x22, Bolt Flang 6x12, Bolt,flange,6x28, Bolt,flange,6x40 are included in the Trx300 Fourtrax 300 1992 (n) Usa Cylinder Head parts fiche.