Easy, just slide the trackball down and put the buttons on top, you can actually hit them with your trackball hand then (if yr playing missile command or centipede you will probably want to use the player one buttons anyway).
Also, I would slide the player one buttons a bit closer to the trackball, and slide the player 2 joystick closer to the trackball, that will put more room between the joysticks and the buttons, making it more comfortable to play.