I've actually repro'd a few sets of these using readily available big-car 401 mounts (cut the motor side off for reuse and discard the mount side) plus a piece we custom fabbed in our shop - sent to Steele Rubber whom I believe has the only mold for redoing these and they came back looking just like the real thing. I have a set on my car and they are holding up great to the 4 speed so far. Cost ends up being well over $100 set, so I didn't think there was really a market when it's so easy to send originals to Steele for revulcanization.
Pat