I found one (used) online at ebay. Was around $30.00. Popped out the old switch , put in the new one and it works fine. Took all of 5 minutes. Had it repaired for summer 2009 season and it is still working.
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Your Ride: 2001 Z3
I find ebay good for most things like that. I bought a set of sliders for my drivers-side window... now I just have to install them! I'm kind of nervous taking off the door panel with that air bag in there!