Parts such as the Seat (vz800): Plate,seat Fr, Seat Assy, Cushion, Nut are included in the Vz800 Boulevard M50 2006 (k6) Usa California (e03 E33) Seat (vz800) parts fiche.
The most reasonably priced component used on the Vz800 Boulevard M50 2006 (k6) Usa California (e03 E33) Seat (vz800) is the Cushion(11.5x22x20).
On this parts fiche the Washer(6.5x24x1.6) is the most specified component.