Try with Major Knight at Mojave Outpost. I think he makes an discount if your NCR fame is high.
There is also a follower on black mountain i think if you tell him you dont want him to be your follower you can go to his building and he can repair your stuff to 100%
That's right. His name is Raul - if you dispatch him to Black Mountain or his Shack he will be able to repair anything. However, he won't have the paid caps in his inventory.
Raul Tejada and Paladin Sato have the highest repair skill of all NPCs, both with 100; Paladin Soto/Sato (Whichever) appears at the BoS safehouse every few days, while Raul is a recruitable companion.