Thanks Serge,
Dave47tuc has already directed me towards Andrews and I rang them today. The Celestron version from Andrews is $299, and $316 from York Optical. Dave suggests that the EQ3 version from Andrews is just $199, if I don't get anywhere tonight I'll call Andrews again. Dave had a set of the EQ4/5 motors which he advised do not fit the CG-4, he should know, I bought the mount from him!
I'm currently tracking some possibilities on CN and Astromart.
I'm wondering if anyone has come up with a reasonable DIY solution, I'd much prefer to spend my money on another decent eyepiece!
Cheers
Chris