MarkT:
If the stepper is 12V 100mA is has 120 ohm windings and won't gain any benefit from
a chopper driver like the Easy Driver. It won't be capable of high speed operation.
Can't you drive it with 20 or 30 volts with the EasyDriver?
I have the SM-42BYG011-25 motors which have a 12v 0.33amp rating and they certainly work better with 24v through a Pololu A4988 stepper driver board.
...R