As long as it sews/runs ok the Singer would probably be your best bet, in my opinion. They are well built and parts (feet etc) should be cheap. The motor setup on it looks like it may be variable speed rather than a clutch motor, if so you could use a VFD, as Gerry suggests, to run on single phase. Just set the VFD to a fixed speed and use the variable speed in the motor control unit - I think it should work.
Otherwise just buy a servo.