Steve..
There's a guy here in Houston that does potmetal/pewter and actually can fix the items... But, as with any potmetal, you run the risk of more bubbling if it has started... Usually the bubbling is a function of the casting and whether or not there were air pockets.......

I'll try and find their website.. They did my check moulding and original door handle for the hemi Charger. I'm taking my wing window frames to them as well............