One possibility is to get a Shimano adapter clamp. They are available in 31.8 mm (1-1/4") and 34.9 mm (1-3/8") and then take braze-on front derailleurs. A braze-on der is slightly cheaper so the combination costs only a little more than the derailleur alone.

The beauty of this is that if you remove the derailleur for cleaning, you don't upset it's alignment as long as you don't remove the clamp. Makes overhauls less tedious.