I'm not sure how large-breasted you are, b/c depending on your size, you either have a variety of options or very few.
For example, I'm now a 44I (crazy, I know!). I haven't found too many in that size, but of the few I found, here's what I use:
For days when I'm just running errands, visiting other mom friends, and in general not too concerned with the fact my chariots are going to be swinging low, I wear the Fancee Free Extra Support Nursing Bra
. It's all cotton and has no underwire. It's comfortable, but for breasts my size, not particularly supportive. I do like the nursing clasp, however; it's a metal hook, so it holds well and there's no risk of the panel popping open.
For days when I'm working and need my boobs to look a bit more well-supported, I wear the Elomi Molded Nursing Underwire Bra (style 3912). The cup sizes are European, so I wear a 42G with a back extender, since they don't make a 44G. On the plus side, it gives pretty decent support, and although its nursing clasp is plastic, but so far I've never had any problems with it popping open. On the down side, it does have an underwire, so, if, like me, you tend to get plugged ducts, then you want to be sure to take this bra off as soon as you can. Additionally, I find the clasp can be a bit more difficult to open & close.
Hope that helps...happy bra shopping, and Congratulations!