I think the last time I bought some, I snagged a couple from Ribble:

https://www.ribblecycles.co.uk/campa...only-cg-cb009/

But, that is a good point about the Jagwire cables:
https://www.niagaracycle.com/categor...100-campagnolo

I just stocked up on a bunch of miscellaneous cables, but I think I skipped the Campy shifter cables. I might think about purchasing and breaking up a box, although re-shipping would still be around $10.