Well- I wrote this post a while ago, I just dredged it up to post here so maybe it'll help some other people =) While it is old- it's still, technically, up to date =)
Ok my lovelies- time for a lesson in larger bras sizes. Here are the stores/website to frequent:
-Wizard of bras ( http://www.wizardofbras.com/ )
They have larger sizes (up to N cup in some brands even) and very helpful customer service- using their online form they got back to me in about 4 hours. They're based in Monrovia, CA
-Bravissimo (www.bravissimo.com)
They have larger cups sizes (up to KK) and good customer service. They're based around London, Glasgow, etc and have several locations.
-The Bust Stop ( http://thebuststop.stores.yahoo.net/)
They have larger cup sizes in pre-made bras (up to M cup in some styles) and do custom made bras up to ZZZ. Haven't tried their customer service, but they list a phone number on their site, and phone is obviously a very good way to get immediate answers. Based in Tulsa, Oklahoma.
-Snares of Venus ( http://snaresofvenus.com/)
If you've got a good chunk of money to devote to getting the perfect bra- this is your place. They do in-person breast molds to keep on file to pattern a bra specifically for you and your body. They obviously do custom sizes up to forever. Their customer service is excellent they list both a phone number and have an email form on their site. They're based in Bakersfield, CA but they will travel to LA and Orange county to do private sessions for breast molding.
-Birth and Baby (http://www.birthandbaby.com/)
Larger sizes up to what appears to be K cup (possibly larger). Unsure of customer service, thoguh I've known several girls who love their bras. Phone number listed on their site. Largely nursing bras, but sometimes when you're incredibly well endowed, it's not a bad option. Based in Lind, WA.
Again, that's just a quick run down of the top spots I've found, there are sure to be others out there that are good.
Now for the real trick: gettign the right size.
First, I know they say to measure under your bust for the measurement, but a more accurate measurement will always be found right under your armpits, above the bust. Thats your band size. The tricky part is to be wearing something that fits correctly. If you're wearing a bra that lets your tits go to your knees, you're not going to get the right bust measurement. So the closest thing you have that fits reasonably well is what you should wear when measuring. Each inch of difference is a cup size, depending on which manufacturer you go with, you may be a JJ or a K. Each manufacturer is different and this can be tricky.
Another little known fact is that cup sizes are not all equal. A D is not always a D, sometimes it's a DD or an E even. The larger the band size on your bra, the larger the cup is. If you're having trouble finding a cup size that fits you, try gettign the closest one you can in a bigger band size than you need, then taking in the sides. The cup size is bigger on a 50 inch band than it is on a 36 inch band.
Getting a flattering style for you is also important, but, as you get higher in the alphabet, the styles tend to become more and more industrial. If you're looking for a pretty, supportive bra for a really large size, you can do one of two things: commission one, or make it yourself. If you're not good at sewing or crafting, stick with the former, however, if you're interested in trying your hand at bra-making, the I suggest taking a look at : http://www.bramakingsupplies.com/
Hope this helps <3