There are actually two pieces. There is a black flap that is stapled to the inside of the cab to the back of the marquee box area, that flap covers the top portion of the monitor space. Then the monitor itself has a black bezel around it (like Level42's pic) spanning the inside of the cab sided to side, and bottom to top, with that black flap over the upper portion. Both are constructed of thick black cardstock paper.
It's tough to explain. Hopefully that makes sense.