6-10 rpm might be a tall order, but you could try this company , they supply robot wars equipment ............
The big cheese robot co.
and for gears/belts you could try
HPC engineering
if you send your address to HPC they will send you a free and very comprehensive catalogue,
hopefully you`ll be able to do something with your dustbin dalek
have you tried running the wiper motor on 6v ?, there is another supply company i had in mind but at present their name/web address escapes me .
