RadCity 3 Step Thru motor sensor replacement

[treetree]

Howdy!
I have been in contact with rad city about my bike not applying power the the rear tire and they figure that the motor sensor isn't working.

Does anyone have an idea on how to
1) replace the rear wheel sensor (and with what) or
2) replace the part housing the rear wheel sensor (and with what)

Rad said they could provide an entire new rear wheel for $350 but that is not something I can afford as a college student.

Any assistance would be greatly appreciated!