There are several companies that do it with good reputations.
The Flying Dutchman has been around for decades. He rebuilt mine a few years ago. Great job.
Then and Now Automotive is another quality rebuilder. They rebuild just about every car part you can think of.
Water pump rebuilder and seller of antique water pumps for all makes and models
Flying Dutchman
Wade Jenezon, 650 Upper River Rd
Gold Hill, OR 97525 USA
1-888-595-1110 Outside the U.S., 1-541-450-2277
http://water-pump-rebuilders.com/Then and Now Automotive
447 Washington St
Weymouth, Ma 02188
Ph: 781.335.8860
Fax: 781.335.1925
https://www.thenandnowautomotive.com/auto-parts-store