Jack,
Sorry that you seem to have had the run around getting a spring.
If ever you have this problem again, please do not hesitate to get in touch.
Mark Wallin of the lock makers York & Wallin is local to me, a friend, and helpful.
He will make any leaf spring to pattern or drawing.
The fact is many of the old craftsmen from the British guntrade are still active and working from home, you can still get anything made here if you know where to look.