There are two New Zealand companies that are making non-underwire, pretty nursing bras: Womama and Hot Milk. Even if you were an underwire fan in your pre-baby life, it is best to go with non-underwire for your nursing bras. Underwire can cause block ducts which lead to mastitis. Even if you are big busted, you can still find support without the wire. (Another note on underwire, I put on an underwire bra this summer when I was back to my normal size, but still nursing and my boobs reacted immediately and got engorged.) They are in shops in New Zealand, Australia and the UK and available online to US customers (and other places) through Zodee. You get a 5% discount if you become a member (it is free) and the shipping cost is reasonable to the US.
The cost of these bras is listed in Australian dollars with an estimated US dollar value. They are on the pricey side, but your nursing bras need to be work horses, especially the first 6 months when your breasts are at their fullest and your baby is nursing the most. I bought some Medela bras (great one hand closure) and they were very supportive and comfortable. They look o.k. but aren't that exciting or pretty or fun. I wore my Medela bras day and night for over a year and they held up nicely. After my breasts had returned to normal, pre-baby size, I bought some Target nursing bras. Within a month, they were looking as worn as my Medelas. It is worth investing in at least 2 (I recommend 3) nice bras and then as you nurse less and your boobs get smaller, you can get some cheaper bras. Some people like to get a nursing sleep bra as well. I just wore my Medelas, but it is about your comfort and how things fit you best.
Of course, if you are very small busted, you might be able to get away without a nursing bra or with a cheaper one, but I do think nursing bras make things more convenient no matter what your size.
The Zodee website suggests going down a band size in Womama and if you are really big busted, up a cup size in Hot Milk. So I ordered 10C (Australian size) in Womama and 12C (Australian size) in Hot Milk. I was a 34C in Medela nursing bras and am probably a 34 B in non-nursing size. Many people have to go up a band size and a cup size. It is good to get measured towards the end of your pregnancy for a more accurate guess. I tried on various sizes and 34 C is what fit me best. I am hoping these bras fit because I hate returning, but I will have plenty of time to exchange if I need to. I will also report back on the accuracy of fit suggestions once I get them and try them on.
E from Blacktating reminded me about the Condessa line of bras as well. The other thing is the Veronica line has underwire. The Cassandra line does not have underwire and that is what I would recommend if you want to try this line.
Elin brought my attention to nursing bra compatible shapewear called Slimpressions. It is designed to smooth out back fat and tummies.