I just went to the HerRoom site out of curiosity. The cup sizes on that Universal Cup Sizing chart seem to start at D. OP says that she is an A CUP. I understand her pain, because I'm an A cup, too. But I don't need the larger band size that she needs. And I agree with everyone who suggested a bra extender. That's what works for me - if I buy a bra with the band size I need, the cup is too big. And no, we A cups can't "go down a cup size" because we're already at the bottom, lol. So I go down one band size and use a bra extender. That gives me a perfect fit. BTW you can also buy bra extenders where sewing supplies are sold, like JoAnn Fabrics.
"Breathe in, breathe out, move on." Jimmy Buffett