Any alternator shop can wind a heavy duty starter. We have an automotive electrical shop in town. He makes anything you need.

 

before you yank the starter (they are a bitch to remove), try shorting across the solenoid and battery terminal on the starter. this should engage the solenoid, but not the starter itself. if it engages the rod, then the solenoid is fine.

I found starters here locally for $200. we have a few shops around Phoenix that will rebuild it with a 12 - 24 hr turn around time for about the same as off the shelf.

please post pics of the engine compartment and battery set up.