The Itallian buffalo is by no means extinct. It is still possible to find proper buffalo mozarella, but you might not find it in your everyday supermarket. If you can find it, don’t waste it on pizza! It’s delicious with tomatoes, basil and a splash of olive oil.
More info here.
(On pre-view I see that Desmo beat me to it with the very same link that I found. I guess he knows about google.)