I'm "well-endowed" also, and usually just go with a sports bra (Panache 5021) under my jerseys. It provides plenty of coverage and support. I also have some Craft Superlight sleeveless baselayers designed for use in warm weather that I occasionally wear. They're supposed to help with evaporation. But it's just so darn humid here during the summer that I'm not sure how much they help. Maybe this is what you're looking for?