When I had to replace a broken spoke for my Fulcrum Racing Zero wheels I contacted Campagnolo-USA directly. They are located in Carlsbad, California.
I love my Racing Zero wheels. I have the Racing Zero Ltd. Edition on the C59 and the Racing Zero Nite on the C60. They are light and the hubs are bomb-proof. But initially, sourcing the replacement spokes was a PITA...until I finally went directly to Campagnolo.
One suggestion, buy extra spokes as spares.
Good luck and ride safely.