The most expensive part in this assembly is the Seat,double.
A sample from the products for the Seat include: Screw Cross 6x10, Bolt,hex 6x16, Bolt,hex.,6x12, Nut Hex 6mm.
The most reasonably priced component used on the Cb500k0 Four 1971 Usa Seat is the Bolt,hex., 6x16.