Thomas
At a push, go to your local motor factors, but take the wheel cylinder with you as there are several different threads. They should be able to make one up for you. Most local garages will make one up for you. On that age of motor you should really check the rest of the pipework carefully.
Failing that, if you want to bring the cyliners through to Larbert, I'll see what ends I have and make one up for you
DUNCAN