Simon,

I think I have one you can have its a good 2nd Hand version i'll check later....but there is another way around the problem...some wont like the idea but you can modify for little cost the back prop to take a normal transit flange then put the mating flange on your box....it removes the bush....some will say it has adverse effects but most uprated boxes run this configuration anyway....

I'll have a look for the doughnut if you still need one...

Regards

Ian