Hi Whopper,
I recently bought a broken Microdrive off eBay, with the same idea as you (though for the Spectrum rather than the QL). However, I thought I should make some effort to try to repair the drive before discarding the innards to the bin and (sadly!) a good clean and re-seating the pinch roller and I got it to work.
So, in the end I didn't buy a vDrive though did get a working m/drive for £10 from eBay. Hopefully you'll have more luck

.
George.