If you have the originals, you can get them rebonded by a rubber specialist. I have used a guy here in WA and he was very helpful.

As for originals, they don't exist as new stock. You can trawl ebay for NOS, but that's about it.

Anything that is still around now is 45year old rubber, so even if it is intact, its not going to be in the best shape.

I have put a bolt through a mount before to keep me out of trouble and it worked like that for years.

I don't think it would be too hard to make up the angle bracket bit and use std 1200 mounts.

I have tinkered with the idea, but have not yet needed to.

If you get really stuck, send your damaged ones to me, and ill get them done locally here and send them back.