I have a 1990 Bianchi Boardwalk that's a particular sentimental favorite of mine. The trouble is that the front derailleur, made by SunTour, is irreparable and apparently irreplaceable. The bike has been sitting in the LBS for almost three months now without result. I've made it clear that I have no objection to installing a brand new front derailleur, but they claim there are none that will work.

This just doesn't sound right. Do any of the expert wrenchers here have any advice on what might fit?