I discovered by lucky accident after surgery years ago when I weighed a lot more that a pleated, Viking-style "apron" does a pretty good job of providing moderate support. It isn't perfect and I wouldn't want to do jumpy jacks in it, but it helped a great deal and did provide some support, and so did a pleated underdress.
Now obviously, you don't want to go around looking like a Viking Lady, but a modern "jumper" (USA) or "pinafore" (UK/Irish English) is very similar to a Norse over-dress. In fact, since I made mine the one in question over 20 years ago, they have found really tailored versions that hug the chest and some with pleats (some in front, some in back) so my guess is Helga figured out pretty quickly how adaptable this style was, even for the "mature" Norse figure.
So I would look for a jumper pattern with pleats and either make a few Spring dresses and/or tops based on the designs - make one and see if it works.
The other suggestion is longer term and probably more expensive, but if you know a good historical corset maker, have someone measure and make you a 16th or 17th century style corest (not the Victorian nightmares). They are designed to provide bust support and made correctly and to fit you exactly are amazingly comfortable.
They were not designed to hide and squish the body the way the later Victorian ones were, just to shape it a bit and provide bust support when the fashioned were to "display the plate."
These days I mostly wear stretch bras that have pads in them, they wouldn't work for a sheer blouse or something but they are fine for support under t-shirts and sweaters.