My guess is that the metal was turned and then formed into the shape; therefore, you could try that route if you can find an independent metal worker. There are some magicians out there and using the original as a basis for a wooden blank to hammer a new piece from could be a last ditch effort.
However, far easier would be calling all the UK breakers. There are more than a few Aero S1s that were written off and I’d be surprised if you didn’t unearth someone with that piece sitting on a dusty shelf somewhere!
Also, have you tried calling Melvyn Rutter? If he doesn’t have the part, perhaps he can suggest a source.
