Unos amigos mios en España estaban discutiendo ... oh shit, sorry
Some spanish friends of mine were discussing the same subject some time ago. One thing seems to be that originally these 6 "rubberpieces" were vulcanised together on a metal plate or something like that. So one cuestion is if 6 solo pieces could do it as well. The probably most important question is the material. Pedro (not the one here

) was sugesting
Vulcolan 90 SH that should bear very high pressures. It is not easy to mecanize. To his opinion it could help to freeeze it down before mecanizing. Perhaps water jet cutting is the way to go. There are rumors that Lambertini once was mentioning that this material was used by Cagiva in the beginning and then they changed to that black stuff that tends to dissolve itself.
Have a look at the datas of this Vulcolan 90SH, it may be worth a try

All the Dart-, Coguaro- and other extern-starter-morini- drivers all over the world have the same problem with this shock-absorbers that can become a real big trouble.
I myself do not have any starter of this anymore. The two I had I donated to some friends who had problems with their legs and were about to quit with morinidriving.
good luck!
norbert