There are tons available, either suction cup, rollbar or using this design with 1 or 2 seats. Personally I just went to home depot last night and built mine for $20. Added some rubber padding for stabilization, and a swivel and tilt camera mount for aiming it just right. It still has a little vibration and it doesn't exactly look pretty, but it worked really well.
I don't want to steal this guys thread with competing products or diy projects, so if you want more info do a google search or pm me.
The 1 headrest design is a pretty common and seems to work. This carbon kit i'm sure looks great, is lightweight and pretty sturdy.