Hi Ron, what about trying one of the speedometer specialists who work on old British speedos.
Magnetic Clock Repairs, Chris Andrews, 07771 515118
Smiths Speedometer Repair, Mick or Jim, 07757 371462
A.E. Pople, 07824 884434
A Gagg & Sons 0115 9786288
Worth a try, as if they can't help, maybe they can point you in the right direction. There was a period a few years ago when MOT centres in NI were really fussy about the subject of mph and kph on speedos, but I've noticed in recent years, that they don't even look at speedo or ask about it, so personally, as long as your headlamp points the right way, I wouldn't worry about it