I have posterboard (or something) from Hobby Lobby (or somewhere) that is off-white on one side and black on the other (the off-white doesn't absorb so much heat from the sun, and the black matches my interior, plus I figure that however it's made adds opacity. I cut this out in the shape of the top of the window and slide it between the glass and the seal when I need a side visor. This works great; it's opaque and can be set up and removed more quickly than anything that sticks on / peels off. When I remove it, I flip it around and it sits between my seat and the center console (works great with the all weather mats to keep it in place, don't know if it would work as well without them). I made one for the passenger side as well, though I seldom need it. Rarely, perhaps when it has been humid, the cutout will curl slightly and touch the side of my leg. When that happens, I simply swap their "storage positions" (or put the driver side one on the passenger side between the console and the passenger side one, depending on whether the passenger side one is also curling) for a day or two in order to straighten them back out. The only drawback to this is that it does scratch my window film (tint) over time.