If you go to the thread, “DVR won’t turn off”someone posted their steps to reduce heat. They drilled holes in the metal heat plate of the DVR, and added a little 12 volt fan (I wonder if it was JUST a computer case fan).
I don't think heat sink tape will last, considering all the vibration and movement over time, and of course the heat. Thermal epoxy would be the permanent choice. I'm also toying with the idea of using an old external hard drive case with a built-in fan. It will take up room of course, but will also offer some protection to the camera connection ports, where it has been reported by one person that the screws came out. I would be mounting it inside the rear trunk of my Goldwing.