I made one out of Reflectix. Had to make it in two pieces and used packing tape to join them together. Works real good and fits into the corners very tight. I laid the Reflectix on the outside of the windshield and was able to cut it along the windshield gasket by feel. Did the bottom piece first and the windshield wipers held it in place while I was cutting it. Then left it in place and laid the upper piece on, overlapping the bottom. taped the joint and cut the upper piece. Worked great.