If you can find a reputable shop that has experience with zinc welding you could ask them.
The trim rings are made of zinc commonly called pot metal.
Zinc flows at a lower temperature than most alloys, so care has to be taken with not too much heat.
The late gentleman that Mike mentioned who used to restud them ( probabaly repaired close to 60 trim rings over the years )
would heat the stud area and build it up with the zinc rod till hard, then dremmel down to size and rethread.
Finished they were same height, size and material, undistinguishable from originals.
Same process can be used with most nameplates or badges that have broken studs as most are zinc based.
He repaired many of those as well.