You might also consider a 3 phase AC motor with a VFD. Something like this:
Surplus Center - 1/2 HP 1725 RPM 208-230/460 VAC 3PH MOTOR
for fractional horsepower motors, there are a lot of VFDs that will take 120 in and put out 220 3 phase:
Adjustable Frequency Drive, Teco VFD, Phase Converter, Variable Phase Output
If you go this route, prefer a 1725 rpm motor over a 3450 rpm motor (of the same series) and gear accordingly. The manufacturers normally put the same bearings in both so you can run a 1725 rpm motor at a higher frequency without having to worry too much about the bearings. Of course you have to consider things like heat and duty cycle but that is the case with all motor setups.
If it fits your budget, it might be a good way to go.