Here are some examples of Tankini tops that come in size 40G Swimwear - 40G - Brastop

You can find the matching bottoms in different sized on the same site. I have the same problem. I'm a 36 GG-HH and I wear a 12-14 bottom...I think a tankini is what is normally suggested for us that are differently shaped.

Swim wear for those of us large busted women is out there, but it usually isn't cheap. I find bra stop to be a bit cheaper than some American retailers. Zodees in Australia also ships internationally, and they have some options for the larger busted as well.