Sorry to read this Rene, I don't know the answer but Keith at BHM will, I think he is still around if not someone there will be able to help you I'm sure with good advice.
Good luck.
Hello Richard,
in cause I travel Britain to buy my MOG from Sarah and Keith and also do some miles for the service there, I asked him this morning.
The first time in my MORGAN live he couldn‘t help. But if there isn‘t another way, a mastercylinder is at the shelf.
Greets René