It's Campagnolo not Shimano!
So you should be able to get the spare parts and a rebuild if you go to your nearest Pro Shop http://www.campagnolo.com/jsp/en/proshop/index.jsp
Tech documents to identify your parts are here http://www.campagnolo.com/jsp/en/doc/doccatid_3.jsp
Alternatively this guy offers independent rebuild if he's still in operation http://www.campagservice.co.uk/rmech.htm
@Oswald started
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It's Campagnolo not Shimano!
So you should be able to get the spare parts and a rebuild if you go to your nearest Pro Shop http://www.campagnolo.com/jsp/en/proshop/index.jsp
Tech documents to identify your parts are here http://www.campagnolo.com/jsp/en/doc/doccatid_3.jsp
Alternatively this guy offers independent rebuild if he's still in operation http://www.campagservice.co.uk/rmech.htm