I have the Italian cultures from All Products – Sourdoughs International
Got it over a decade ago, and keep it alive in the fridge. Have made some awesome pizza with it. I actually ought too wake it up, it’s been while. Waking it up after a long dormancy takes 3 or more days. Learning to care for it is bit of process – definitely more trouble than commercial yeast, but the flavor is sooo much better.
Edit: I wanted to add all those “make it yourself starters” are bit a gamble. Although technically there are yeast and stuff in the air, you don’t need to waste time “catching” them. There’s yeast and bacteria already in the flour. It’s going to depend where that flour came from and a million other things. The biggest problem with 3rd party starters is activating them because YOUR flour is contaminated and the starter needs to establish dominance.