I have found that Asian clothing is often much smaller in the bust than comparable american sizes. Banana republic petites, other than being cut shorter, are also cut smaller in the bust then their regular clothes. Other than that, I don't know where to get shirts that are cut unusually small in the bust, especially now that I've put on almost 10 lbs. I'm still relatively thin, but my bust measurement has literally not changed at all as I've put on that weight, while my waist has grown by 2 inches. While that may not seem like a lot, it means that shirts that fit me in the waist are now way too large in the bust. That has always been true, but always becomes a much bigger problem whenever I put on a few pounds. I wear small or even xsmall tops, and I wear a 34aa bra.