Because the stock Phantom 2 Vision + doesn't have a gimbal, the camera bounces a lot along with the drone. The videos are choppy. Is there a gimbal or something I can buy to stabilize the camera during flight?

Yes....Its called P3P or P4

What mjlstudio probably wanted to say and didn't came out right is,..... ;-) Yes there is but it's almost as expensive as a new Phantom 3 standard or an secondhand Phantom Vision Plus (yours is probably a regular Phantom vision with the egg like camera?).
http://www.rotorpixel.com Or you could just buy a cheap 2d gimbal voor 50 euro (they work fine!) and mount your cam on that or buy a cheap GoPro rip off (70 euro) and get even better footage than you have now,... Probably!

Without a gimbal how do you have the camera mounted? Can you show a snapshot?