If your shifter is truly broken, the best thing you can do is toss both of them and buy a new pair of 2010 Veloce or Centaur Ultrashift ergo levers. The Veloce model is only $120 at Ribble and that includes a new cableset.
I would not waste time and money on repair parts for an escaper shifter. Campy has quit selling individual parts to repair these shifters. The major assemblies that they now sell are too expensive to be cost effective.