@gobblegirl Secondary A+ to Smithers. It's lovely spot!
Lady #2: I am a lady with ...let's leave it at a fairly prominent set of lady bosoms. Along with a good bra (and the back of a safety pin) that many of the other Ladies have suggested, a fantastic thing to look for a in a woman's button down are darts in the front. I have a lovely DKNY one (sale rack of course) and the darts allow the fabric to fit properly across the chest so it doesn't tug and gap.
Straight-line button downs are not the solution you are looking for. An extra perk of the darts is that they'll improve the fit and look of the shirt as well.