Campagnolo front shifters from that era were not indexed. So any front derailleur (double - 28.6mm clamp, bottom pull) should work with the left shifter.
At the bike Co-op I volunteer at, there is probably 10 pounds of such derailleurs that would work - at $5 per. Suntour, Shimano, SRAM road, etc.
Last resort: Ebay; it will take seconds to find a compatible unit. Or last last resort - an open LBS who has some of these undesirable 28.6mm clamp derailleurs in a bin, which hasn't been touched for years.