Our 32" flat screen is mounted on a VideoSecu articulating mount, about $25 on Amazon. I attached one end of a small bungee to an existing screw (window frame in my case) and the other end hooks into a hole in the rear center of the mount. It stays put, well. Probably helps that the TV is somewhat parallel to the direction of travel, so Start/Stop don't put all that much pressure on it. The trick is to keep it from starting to move.
Should add... Didn't trust the walls to hold the base of the mount. I was able to drill through the end of a cabinet that was made of particle board, and fasten with two 1/4" bolts with heads on the bracket and nuts inside. Was
This Mount