Polar Products has created Cool58® Bra Coolers, which are freezable pads that you can put in your bra to help cool things down. Apparently you can wash and reuse the pads, which come in a variety of cup sizes.
The paddings freeze up at just 14°C (57.2°F), so you can activate them in a freezer, refrigerator or iced water. They are also described to have cooling effects lasting about an hour. One set costs US$37.11, a reasonable price for these sweltering times. People desperate to beat the heat can get the freezable bra inserts here.