Some other options that come to mind are solid state relays (SSRs) or developing your own control circuit, using triacs. Both would require more work on your end than a COTS solution. Here is some information from Crydom on SSR basics.
They recommend a random turn-on type for inductive loads such as motors, although they don's specificly refer to using the SSR as a power control device for motors. Probably more like a switch. I don't see why you couldn't use the random turn-on to control conduction time over a specified number of cycles (60 hz) and thus controll the average power to the motor. For example, five cycles on and five cycles off. The timing will be important for smooth operation from your motor. In any case, you want to chop the signal to be in terms of full cycles. Trying to chop faster than one cycle will cause problems for the same reson you can't use a light dimmer on a ceiling fan.