I'd like to trade some of my sourdough starter, which I purchased from Monica Spillar back in the early '90's, for some Ischia. PM me for details.
I'm going to the Ligurian coast this summer and I'm going to try to get a piece of starter from a bakery there or maybe start one from scratch.
you can try this web site. They have sourdough cultures from all over the world. They can also be bought from Amazon and the reviews there are favorable.
Ed Wood, by the way, wrote Classic Sourdoughs, Revised: A Home Baker's Handbook. I'm not sure if he's actually affiliated with the sourdough sales site or if they're just licensed to use his name.
Might be worth giving a try. They have a culture that they state is from Ischia island.