I had no joy with Graham Moag. He did come up with an interesting potential solution (see comment added below).. I reused my races with new balls as they were not too bad. Not ideal but the steering felt fine afterwards.
I checked all i had but I do not have the sizes. I did come across a solution for damaged races a while ago. It involved turning up a circular section donut, to replace the balls. the donut was made of some nylon like material but harder. A liberal greasing and it was as good as the balls. the donut compensated for the spalled and damaged race surface. Worth a thought??