What is the smallest Bra size in B cups?

I measured me . The band the bust and the cup. My cup was a B. What is the smallest size in the B cups? I have heard of 32B but not 30B. I hope there is such a thing as 30B. I Went to target in like march and the 32B bras didnt fit. They were too big. I want a bra that will actually be the right siz.e Not 2 small not to big. Just perfect. I am wearing a 30a right now but its a little 2 snug.