Hi Fraser,
How do you know its an EQ3? Hard to tell without a photo but my EQ3 has a 20mm thick counterweight bar. I think the EQ5 has an 18mm shaft.
Motor drives can be bought, the cheapest is RA only.
http://www.myastroshop.com.au/produc...sp?id=MAS-022G
You could of course do a DIY thing.
Photo is my EQ3 which is also a Saxon brand, made by Synta, with my f5 4" refractor. Great lightweight mounts these, I use mine a lot.
Matt