Aerie's 30 bands run small, so a 30B may work for you from there. Especially in black. The Natori Feathers may also work in 30B. . Reddit·r/ABraThatFits Best Bras for Small Boobs | Top Picks for AAA, AA & A Cups
For small busts (AAA to B cups), the best shopping strategy is to look for brands that either specialize in petite frames or offer extensive inclusive sizing like half-cups. Top Specialized Retailers best place to buy small bras
Places to find extremely small bra sizes? Particularly affordable ones? Aerie's 30 bands run small, so a 30B