For many years ladies have worn cup sizes too small, but then again, larger ones weren't available. Well, they are available now! But many are still wearing bands too large and cups too small and complaining of what a pain bras are. Very well endowed ladies report that they are pain-free as long as they wear the correct bra, so your whole outlook on this topic may change for the better.
C "BIGGER BRAS"
A selection of bras up to at least G cup (some to K cup) from "BiggerBras" shown below:
Large Cup Size Bras up to L cup, from "BiggerBras.com".