Its a drastic solution, but if you're handy with a dremel, you can manufacture new ones from other car parts.
I've already used both a XXX4G+ Front mount AND a HB D4 Rear Mount, as 511 Front mount. Geometry is very close to original and, well, I had it in the pitbox to try.
The 511 front mount is an easy target for a break point during a tumble, and have now taken the step to bond two XXX4 front mounts together to make one mega front mount.
I've danced the car on this one several times, with no sign of fracture or breakage.
It's about 6mm thick.
I know, it's shocking...
But it works!
