please help me find the right component!
Do you need to know the absolute or relative position of the motor? I assume you don't since you want continuous rotation.
You can get continuous rotation servos quite cheap. (hobbyking etc.)
You drive them with a typical RC servo signal but the signal sets the speed, in either direction, instead of the position like a normal servo.
(Technically they're not a servos because they have no feedback, but they're still sold as a servo)
Just get a standard DC motor if you don't need positioning...
If he needs gearing then a continuous rotation servo is much simpler since it already has all that built in.
But if he wants it to be simple to drive a DC motor is easier than a servo which needs a mcu or something to generate the pulses.
Some context would help.
What will the motor be used for? What size load will it be handling?