Hi,
I have one of these (excellent) lightweight rotary machines - from UK Shoot Warehouse - Sillosock Hypalite Rotary (also sold by Bushwear)
See>
http://www.ukshootwarehouse.com/sillosock-hypalite-rotary
Unfortunately, after several years of use and abuse, the 'gearbox' has stripped a couple of cogs.
It's a small unit - about 4cm across, and sits on top of the similarly sized motor.
I've contacted UKSW to see if I can get one seperately and they don't have any - they say all the units are pre-assembled by their supplier and they only order in the required qty to make up the corresponding number of finished units. They were very helpful and said next time they order a batch they will see if they can get a spare gearbox at the same time - but that could be weeks or even months away.
Does anyone have any experience of these or any bright ideas please :-)