Follow up
I fixed mine by drilling holes on either side of the original boss (after removing mirror of course!).
Then I took some SS welding wire and threaded it thru the holes and the spring, winding it 4-5 times and twisting it off underneath. Stuffed the tail up into where the boss used to be and good to go.
Oh and don't puncture the rubber piece it looks to be a weather tight seal.
Pot metal!?
