Parts such as the Oil Tank: Gasket,level Gauge, Body, Cap, Bolt, With Washer (5r2), Lens, Level Gauge are included in the Rd80 1982 12g Europe 2212g-300e1 Oil Tank parts fiche.
On this parts fiche the Hose (402) is the most specified component.
The Bolt, With Washer (5r2) is the lowest priced item on this Oil Tank schematic.