FWIW. Because Shimano has gone to great lengths to make shifting between cogs as efficient as possible, if you don't mind having access to only 8-out-of-9 cogs, you should be able to use a wheel with 9-speed Shimano cassette with your 9-speed Campagnolo shifters ...
You just have to adjust the STOPS + tweak the index to shift correctly between the smallest & second smallest cog ...
Done!
You'll probably lose use of the 6th (?) largest cog, but you probably won't notice its absence.
If in doubt, presuming you know someone who has a bike with a Shimano drivetrain, borrow the friend's rear wheel to confirm ...
If necessary, "borrow" a 9-speed Shimano/SRAM cassette from a MTB if you need absolute confirmation.
If you want to use all 9 cogs ...
If you use a '105' cassette (i.e., a cassette with separate cogs), you can cut shims from a soda-or-beer can (
my apologies for not remembering who to provide attribution for this tip) ... the apparent thickness of the aluminum is ~0.2mm.
WHEELS MANUFACTURING made/(makes) replacement spacers which will allow you to restack a Shimano cassette to Campagnolo spacing. I had a set (maybe, they are still around here, somewhere) ... in a side-by-side comparision, the WM spacers seemed to be (IMO) the
same thickness as the spacers in an 8-speed Shimano cassette ...
As Fate would have it, I ended up never using those WM spacers because most of my wheels had Ultegra-or-XT cassettes & I found that I didn't mind (!?!) using one less cog on the bike which was set up with a set of 9-speed Mirage shifters.
I generally use an HG-53 (or, better) 9-speed Shimano chain.
BTW. I'm currently using 10-speed Campagnolo shifters + 9-speed Shimano cassettes with Shimano rear derailleurs ...
Using either shims or the Wheels Manufacturing replacement spacers increases the stack by ~1.4mm (?) ... so, there's that much less thread which the lockring will engage ... it's doable.
Whichever (if any) alternate you choose, you will need to adjust the Stops & Indexing because the driveside flange of the Campagnolo hub is closer to the hub's centerline than the flange on a Shimano/-compatible hub.