Long shot ideas. Jerry Montgomery designed the Sage 17. I understand Sage Marine, in Colorado, was closed about 2021. You may be able to find parts that fit your boat more easily than the original Montgomery 17 parts. Another idea would be the West Potter boats. They were a direct competitor with the Montgomery boat.
The quickest solution would be to work with a metal shop to have them build you a replacement. The magic of CNC milling could produce a copy that would outlast the mast.
The originals were mass-produced molded units. They were common in the 70's when the 17 was in production.
You might find something that could work in a salvage shop like
SailBoat Parts. They are located on the East Coast. I would look for a spot in California. The Bay Area down to San Diego. There was a pocket of Montgomery boats in Monterey and on Lake Havasu, AZ.
I looked at the Dwyer Site. Sure enoughthey ahve closed their doors. That is a real bummer. I confirmed that Dwyer was the source of mast parts for Montgomery boats. The part you seek was the DH-106.
Here is a listing of possible contacts:
Good luck.
