There's an early middle aged woman who's become a semi-regular customer at my workplace, she's hard to accurately measure because she's clearly dressing to hide breasts, but her efforts are quite futile. I'd have to see her in something other than a minimizer and baggy clothing, but I'd guess her to be in the H-J range though. She's also within an inch of my own towering height. Got a little bit of a 'librarian' look about her.
I'm not single at the moment. Otherwise I'd strike up a conversation with her and find out more.
Honestly I think the best way to date busty women, is to A) keep your eyes open, and B) learn how to approach women effectively. It's not *that* hard, I've got a devastatingly effective track record, even though a majority of women aren't into other women (or at least think they aren't).
Ultimately though, you're dating a 'person', not a bra size... if you get that mixed up, you won't have a very happy relationship regardless of the presence of any superficial trappings you seek.