I am not certain this is your unicorn, BUT, I post this option on every one of these threads. It was the only bra, at any price, that would flatten me and keep me in place when I was a G cup. (I've since had reduction surgery and have more bra options, and I still rotate this bra among others).
It's ugly AF and it's expensive. So what.
https://enell.com/products/enell-sport