Northwest Classic Seat Cover provided an R65 specific replacement cover in classic black. I believe MotoBins also sells covers.
http://stores.ebay.com/NW-Classic-Motorcycle-Seat-Covers Clean off all previous upholstery adhesive. You need a solid foundation for your work. Big box home stores carry an excellent glue removal product, Motsenbocker’s Lift Off.
One of the R65 group mentioned that he was experimenting with some small, nylon U-channel that was originally used to protect band saw blades. He sent me some. This channel fit the seat pan edge exceptionally well, required no bonding and protects the new seat cover from cuts where the material wraps over the semi-sharp edge.
I favor 3M Super Trim Adhesive. It has the highest bond strength available in a rattle can. Shoot three full coats of adhesive onto the pan and the fabric.

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eat masked, adhesive sprayed on pan and cover. Note plastic U-channel on seat pan edge. The cover's instruction page suggested a hair dryer or a heat gun to make the vinyl easier to stretch and fit. Forget about using your significant other’s hair dryer. It won’t generate enough heat to get the job done. A true heat gun is what you need to stretch and draw down the vinyl to where a Marine D.I. could bounce a quarter off of it.
Replace the metal retaining strips using aluminum pop rivets- 1/8 x 5/16 rivets worked well. Possible areas that have a washer under the rivet may need 1/16-inch more length. Folds in the vinyl may also drive this decision.
Just about finished. Tools req'd shown. Trim off any excess fabric. Use a “Lift Off” soaked rag to clean excess glue from the seat pan. Avoid letting the removal juice run under the vinyl to pan bonded areas.