This is a cheap hack, but may be useful to you. I use 3D CAD programs frequently. Navigating three dimensions with a 2D interface (mouse) is annoying. The UI in Pro/E, for example, requires either clicking different modes to pan/zoom/rotate, or holding various key+mouse click combos. The interface is improved by something like these.
You can achieve much the same effect, however, with any USB game controller with two analog thumbsticks. I used a knockoff Xbox controller and joy2key to map the controller inputs. I've set left analog stick to rotate, right stick to pan, triggers to zoom. Now I can perform fly-throughs in one motion.