If you get an old set of band-on down tube levers, either Campag or Shimano (or copies) and remove the levers, you will have exactly what you are after - a set of band-on shifter bosses.
@yoav started
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If you get an old set of band-on down tube levers, either Campag or Shimano (or copies) and remove the levers, you will have exactly what you are after - a set of band-on shifter bosses.