Here's the solution! You've probably noticed how many of the newer 4Runners have black wind deflectors on the back of the vehicle. The manufacturers realized they could keep the rear window clean by moving air across it. So they put those air deflectors on the back to catch the air and help keep the window clear.
Aftermarket a rear air deflector will cost you around $100!!! Why! Make your own for $20 and a couple (at most) hours of labor! Here's how...
These
are the part you'll need. four right angle brackets, one door threshold,
and various screws and small bolts. Cost...$15-20.
Take the threshold and cut the ends at a tapered angle (shape it like the other wind deflectors you've seen on other 4Runners!) Take the angle brackets and bolt them together to make a U. Countersink the holes in your top for the mounting screws, and mount the sucker! Oh yeah...if you want to paint it...do that before you mount it. :-)
Here's
the "pre-painted" finished project.

Here's two pics of how it looks now. I think it should
mount slightly higher than I have it in this picture, so it picks up more
air, but it works great! Even up-close I promise this does not look homemade!