The Betson style trackball will work fine, as will the Happ style. The problem is if you're mounting it in wood, the trackball will sit too low.
Couple of options to consider:
Use the square mounting plate but route out the control panel top so that the mounting plate sits flush with the cp. you can then bondo it to make perfect for art going over it, or if you're using non adhesive artwork and plexi, just cover right over. don't forget to bevel in plexi around the ball.
get a trackball from Ultimarc:
http://www.ultimarc.com/store/section.php?xSec=10this trackball will undermount in wood and still sit at right height.
if you're using a wood cp, consider covering the whole cp in metal. you can then cut out the wood below for trackball mounting and you get one nice smooth cp top that adhesive artwork will adhere nicely too