If it is 1.50" or 1.75", we have a new mount I designed at ChaseCam that is made from billet aluminum and is pretty cool if I say so myself. Otherwise we sell a mount that is designed to handle a range from 1.5-2.00" and is being used on many race cars.
try a clamp-style camera mount from any photography store.
i've had this one on my exige for >14,000 miles and many track days with no movement or other issues. on the street it holds my valentine one with velcro and when i get to track i just put the camera there, secure it with the screw, and tilt it down a bit.