Probably stuck brushes, but could be stuck impeller vane also. Check out this schematic. Your pump should be similar. Fill Rite Series 1200C Repair Kit
Take off end plate from impeller end and try turning the impeller and shaft. This will also turn the commutator on the brushes. May free it up, but just short term solution. Probably needs a rebuild kit. As the brushes wear they begin to stick, and could ruin your armature.
I would start with the Yellow Pages and look for a Fill-Rite distributor. Should be listed under pumps or petroleum equipment. Also might try a NAPA dealer if you have one nearby.
Took plate off the end. Pump and motor turn freely. Measured power to shutoff switch. That switch is good. Was able to measure power to connectors on end off motor. Not sure how you get the bushes out? Are any of the electrical parts replacable under end plate or does it seem like a brush or motor issue?
Checked out the part diagram. Part on end of motor is thermal protector. There is also a rectifier listed. The line switch tested ok. As started the motor and pump turn freely. Not sure how to take brushes out to inspect them.