Look for some # 25 chain,
http://www.amazon.com/Koch-7425100-R.../dp/B004HKITHA Just saw a refence, that scooters use it.
http://www.electricscooterparts.com/chain25.html I have a 9 tooth sprocket for a project, can't remember where I bought it 25 years ago.
http://www.surpluscenter.com/Power-T...1-2742-9-A.axd
Cheers, Neil.