You need a 10speed campag freehub as the campag freehub fittment is the same for 10/11 spd cassettes. Or you can get a 11sp cassette that fits on 10spd free hub, they exist but aren't cheap.
Neither option is cheap.
I'd just rebuilt wheel with new 11spd hub.
Sounds like a good excuse to buy new wheels then :)
@Bezzin started
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You need a 10speed campag freehub as the campag freehub fittment is the same for 10/11 spd cassettes.
Or you can get a 11sp cassette that fits on 10spd free hub, they exist but aren't cheap.
Neither option is cheap.
I'd just rebuilt wheel with new 11spd hub.