I actually discussed this with my wife just a couple weeks ago. I'm a smoker so, if I'm driving for more than an hour, I will need to crack the window for five minutes of the drive, at least. Trust me, its for everyone elses safety! :wink:
I came to the conclusion that even if they made one, it would ruin the look of the car. I also wonder how easily it would be to make given the curve of the top, and the frameless windows.
I have started using the theory: "better me than the speakers" (lots of drops head right for the speaker covers), and I just lean over and let the drops soak me, instead.
But, yeah, the drippage is very bad. Been a long time since I was in a car that dripped inward as badly.