Here's a link to the owner's manual, but not a parts list.
Contact the manufacturer for body parts, the chassis maker for those parts, engine and transmission makers for those, manufacturers of the various systems. Most all found on a search with Google, as I did for the owner's manual. Very little is actually made only for the Mandalay, most RVs are a collection of standard parts common to various RVs.
For used parts, call around to these RV salvage yards.
RV Salvage/Surplus Yards (List) Updated 7/7/15 - RV Forums - myRVparks.com