Parts such as the Rear Caliper: Boot,sleeve, Pad & Retainer Set, Spring,pad, Piston Set are included in the Gsx650f 2008 (k8) Usa (e03) Rear Caliper parts fiche.
The Boot is the cheapest item from this partsfiche.
The Rear Caliper is made up of components including this Caliper Assy,rr which is the most expensive.