Parts such as the Seat (vl800k6/k7/k8): Band,seat, Washer(6.5x24x1.6), Nut, Cushion are included in the Vl800c Boulevard C50 2007 (k7) Usa California (e03 E33) Seat (vl800k6/k7/k8) parts fiche.
In this schematic the "Washer(6.5x24x1.6)" is used most often.
The most reasonably priced component used on the Vl800c Boulevard C50 2007 (k7) Usa California (e03 E33) Seat (vl800k6/k7/k8) is the Cushion(11.5x22x20).