Does anyone know what the piece is called that slides with the shifter? It covers the mechanics underneath. I've looked "shifter cover", "slide cover strip", "shifter slide cover", and a ton of other things to indentify. I'd love to buy just the part and insert it rather than buy the whole assembly. Part is circled in red in attached picture.

 

The whole unit is GM Part # 15137654 Bezel. There is no part number for just that piece.

It's a fairly simple piece of flexible plastic, you could make one if you could get the right width and thickness.

Good Luck!

 

You cannot buy just that piece, it is part of the assembly. As mentioned, easily made with the right material.