I just ordered a moonlite focuser and am going to try coupling a 1.8deg stepper directly to the shaft on one side with a shaft coupler.
But ideal is a small timing belt as that could drive the focuser knurled knob directly.
Steve (Kinetic) made a nice slip clutch
Post #1 here
http://www.iceinspace.com.au/forum/s...focuser+clutch