I relined a batch of torque balls last year.  Bought the mold and information on how to do the process from the gentleman that used to do them for Bob's.  I needed uncured neoprene rubber of the proper durometer and an industrial metal to rubber bonding compound and an oven to vulcanize the rubber.  Bob's purchased most of my relined torque balls, they are available from him online.  I currently only have a pile of cores awaiting relining.  Uncured neoprene (not easy to find) has a shelf life of