If you were a little closer I'd offer to weld onto the broken bolt and turn it out for you.
Ask around for a good TIG welder and see if they can do the same.

In my experience removing countless broken bolts TIG welding onto the ends of them is by far the most successful, and if you're any good at it chances of damaging the part is the smallest by far.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-