"...every Monty I've ever seen has one nipple broken off, at least one."

If you have a thermal vacuum switch with a nipple broken off, I've repaired them by using the plastic tube from either a Bic type pen or a straw from a carb spray can, inserted into the remainder of the old nipple and the small hole in the thermal switch, held in with some epoxy or crazy glue.Usually works OK then!