What you could do is get an 11spd Shimano cassette milled down 1.8mm so that it's fits your freehub, will then work just as well with Campag as a stock cassette.
Or put the freehub body on a lathe I guess? Unfortunately Shimano don't give you the opportunity to spend £300 on a cassette.
Or that
@Lolo started
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What you could do is get an 11spd Shimano cassette milled down 1.8mm so that it's fits your freehub, will then work just as well with Campag as a stock cassette.