[flamesabers]

I would think a high impact sports bra. The reason is that it tightly holds the breast to the chest wall to prevent bouncing.

I concur. Some of the sport bras I've tried makes me look like I have a flat chest again!

Besides visibility, I think something else to consider is whether anyone will touch your shoulders or hug you. Unless the other person only taps you on the shoulder and the bra's straps are wide enough to be mistaken for a tank top, your secret will be out.