San Marzano tomatoes can be bought in any grocery store (Cento brand, for one), and buffalo mozza can be found at any better-than-average grocery with a good cheese section. Buffalo mozza is a bit pricey, but it's worth it over the flavorless wet cow's milk balls masquerading as "real" mozza.
I do agree that AP flour is just fine for dough, it's more about the process and technique there. I do think a blend of AP and bread flour gives the best flavor and consistency, personally. I use Gold Medal AP and King Arthur bread, nothing fancy and in every grocery store...














