I'd say for starters to have your Derailleur hangar Alignment checked by a LBS, just to be safe. Even small differences can do the job.
Many campy derailleurs are rebuiltable part by part, I'm not sure if that part in question is replacable. Once again, a stop by an LBS should be in order as they can check their Catalog... Or if you feel like staying in the comfort/saftey of your home check out
http://www.campagnolo.com/pdf/spares06_A.pdf, that's the 2006 spare part file, Part A. That'll have the parts available listed.
Campy spares are expensive, but less expensive than a new Derailleur.