My sister in law is a fairly large girl up top. For years she couldn't find anything to fit her. Then she went to a company that measures and custom makes bras for women. They don't have stores but have "specialists" that are based in many places all over the country. The woman my SIL saw traveled half way to meet her since she lived too far away. The bras aren't cheap but they're well made and last a long time, at least according to what she told my wife. Might be worth a look.
Zyrra Home | Custom Bras
Zyrra Home | Custom Bras