Real long shot but I tried to help out someone on another forum whose Grandson had a broken car in his slot race set. The pinion was split but it wasn't a standard or FF size and I damaged the motor trying to fit a pinion.
I don't suppose anyone has a car or cars from the set below that they don't want and would be prepared to part with for postage and a bit extra. Even a rolling chassis would do as the body is fine.

Tire Land vehicle Vehicle Wheel Car

Tire Wheel Vehicle Car Hood

The gent was very appreciative that I even tried to make a repair but it would be great to have a happy outcome if anyone in the UK can help.