[QHriderKE]

For a rear cinch, if I didn't want leather I would probably get a mohair one that's woven a lot like a front cinch.

As long as the leather is sound (no serious signs of cracking or stitching coming loose), you can give it a light scrub with a soft brush, saddle soap and water before applying a light coat of neatsfoot oil.

If your saddle is leather, I think nylon or biothane would look unmatched and tacky.