just recieved a 46mm adapter from nextphoto-http://members.rogers.com/nextphoto/order5400.htm
Using a 46mm circular polariser on it. Exactly as it says, no vignetting at 28mm wideangle. Nice and small, it clips on and fits great. Just remember to read instructions and follow to the word, extend the zoom fully and hold the lens barrell while clipping it on, to make sure you don't put undue pressure on the camera lens motor.
Good idea to leave it on, with a 46mm lens cap on top, and just screw or unscrew any filters as you please. It's small enough.