Montesa Cota 300RR Fuel Pump Advice

I have a 2016 Montess Cota 300RR (MRT300G) with running issues that I have narrowed down to the fuel pump. We replaced the gas in it but due to the shape we weren't able to see very deep into the tank. So we chased our tails a little bit on other issues and eventually got frustrated and put a strap on it and pulled it through the parking lot hoping to get it to start and got it to fire a bit, which is more than what we had at this point. Now due to the foul smell of bad fuel coming from the machine we figured it just took that much to get all of the new fuel into the lines, but it still wouldn't start. Sprayed some stuff in the airbox, kicked it good and it started up. So next I took out the fuel pump and its very rusty and corroded, fubar. After putting the machine into the computer and pulling up a parts fiche we found the pump (16700-NX7-003) but the dealer price is $522.18 and retail price is $949.43. The customer has asked us to do everything we can to rebuild it rather than replacing the assembly. However we cannot seem to find rebuild parts for this pump. I am hoping someone here has worked with something like this before or has a connection that can point us to proper rebuild parts. Even if someone can point us to a more common machine (crf, yz, anything a bit more mainstream) that contains the same pump motor we can then plug that into our rebuild kit dealers and work with that. Any help or advice is much appreciated.