check out EBAY often they show some good deals. HOWEVER I would only consider NIB or new in the box listings, Older models such as O. S. FSR and FS series engines are common that are fine motors. do your research and DON'T overbid.

Also look at the KANKGE SK 50 it is an ABC ball bearing and is $60.00. I have the 90 and its super (slow to break in and slow to wear out)