Doesn't Moving Comfort make a lot of plus-sized gear? I'm not sure about cycling stuff, but I know they make tops and bras for running and the gym.

I've heard good things from my plus sized runner friends about the Enell bra. Women who are in the 38 - 42 DD range rave about it. It's probably more heavy duty than you need for cycling (less bounce, I guess ) but might be worth a look.

Title9sports.com has a good rating system for their bras. They have little barbell icons and each bra is rated based on size and activity.

Again, good job on getting out there!!!