Bob33
Unfortunately I had that problem too but all I did was cut cown a bodyclip to size cos I couldn't find a part number either! I did contact Schumacher UK and Chris Ashton recommended stripping down the shaft, greasing it and then threadlocking the grub screw back in (aparrently its this being a little loose that causes the pin to vibrate, snap and come out!) but he couldn't give me a part number either.
Anyway, its seems to have solved the problem, I've not had one break since.
HiH
Paul