Hi,
The change from 11S to 10S requires the change of only a single part ((but it's no longer available as a spare (if it ever was)) of an upgrade/rebuild kit with Campa reference EC-CE110.
No one seems to carry stock though as it's not been around for long anyhow.
If you can find it then that would be great for other people running the original 10S shifters with the new 11S bodies as well.
Me I think I may simply buy the replacement body kit (naked shifter without brake lever nor hood), pop out the brake lever of a 11S (whichever I'll get), put that in the spare body and put a hood on it. That's really all it takes but it ain't exactly cheap. (Well, it's not that bad considiering a single Campa screw could cost a tenner a pop anyway....)
It's only going to be used for a few years at most so it's really not that big a deal. Even a set of Centaur Powershift shifter won't break the bank either.

In the pic you'll see part EC-RE017 and that's the only part that determins the number of clicks of the RH shifter.
RE stands for Record so I guess Campa must have had plans to market these new shifters as 10S across the entire range at some point....
Thanks for offering your help anyway.
Ciao,

Being a snob is an expensive hobby.