Lexan windows and ports were once cleaned on board with toothpaste (not gel) and elbow-grease (lots of it) but have since found a product that works well.
Intended for automobiles, it removes yellowing, restores optical clarity and eliminates haze on headlight lenses.
Follow the directions but the trick is, don't apply it in direct sunlight, only work a small area and... a little dab'll do ya!
Blue Magic Headlight Lens Restorer: http://bluemagicusa.com/index.php/bl...c/products/101
Found at Advance Auto Parts (in Fort Lauderdale, FL) for $5.99 and, no, I do not have shares in either company.