Check Lowes for Coolaroo window shades. They come in sizes ranging from around 72 to 120" and range in price from around $60 to $100.00.

I have installed a few of these shades for people in the past few years and they seem to like them a lot. Best thing about them over using something like a trap. They can be rolled up onto their own frame when not in use.

If you go this route. Pre-drill the screw holes and buy stronger screws. I have broken a few of the screws supplied with the shades off when tightening them.