Well, I was gonna say check the Owners Manual before I clicked your post but...
I can't find anything handy on it either that's conclusive, but the most common location seems to be if you pop the hood open, and look just in front of the windshield on the passenger side, and look for a long rectangular part that unscrews and lifts out.
I do see that Autozone has them, sold in pairs;
http://www.autozone.com/N,14200647//shopping/partTypeResultSet.htm
This should get you started, but you'll have to enter your Year, Make, Model and Engine from there, then your zip for a price.