I'm big-boobed, but not plus-sized, and my favorite nursing bra was a regular, well-fitting bra I bought at Nordstrom and had their alterations department switch to a nursing bra. Also, be aware your band size will increase during pregnancy, but will usually go back down to the normal size by about 6 weeks to 3 months postpartum. It's usually recommended that you not be fitted for a nursing bra until at least 2 weeks postpartum to give your milk supply/boob size some time to regulate. Even then, I would consider buying a smaller band size (where the cups fit properly) with a band extender so it will still fit you when your ribcage shrinks back down. But I also know how ridiculous it is trying to manage two weeks without any proper support. So you may try to find a cheaper sleep bra or nursing tank to get you through those first few weeks. I'm not sure what I'm going to do this time around, because last time SUCKED until I got a good bra - which actually didn't end up being until a couple of months in. (I got an okay-ish one at 2 weeks.) My first okay bra was a Medela. They aren't bad, but mine wasn't quite properly fit, and they don't actually really sell my size (32F at the time), but that shouldn't be an issue with bigger band sizes. The one that was good was an Anita that I bought off Amazon. They have a HUGE range of sizes available.
The biggest thing is finding a place to get truly, properly fit for a bra, or measuring yourself to get a good fit. Motherhood says they will fit you for a bra, but told me I needed something ridiculously off of my true size. Many department stores are the same way, unfortunately. This page
has a decent, though complex, self-measuring tutorial. When I worked for a lactation consultant (we also sold Medela and Bravado bras - I know lots of people who love Bravado, but I never found one that worked for me), we used a much simpler method - put the tape measure along where the bra band goes on your back (do NOT do this while clothed, or wearing a bra, though - do it topless), pull it under your armpits, across the very top of your breasts, and make sure it is very snug - it should pull your breasts together a little. This is your band size (round up if it is an odd number). Then, leave the tape measure across the bra-band area of your back, and LOOSELY pull it around your breasts at the fullest point - usually around the nipple line. DO NOT pull it tight - it should just sit on your boobs without compressing at all. The difference in inches from your band size is your cup size - i.e., if your band size is 38, and your bust measurement is 39", you're an A cup, if it's 40", you're a B cup, etc.