WANTED: motion sensor

I am working on a project to make my own "scarecrow" that uses a sprinkler to chase critters out of a yard. It uses the motion sensor from an outdoor security light like the one you have in your driveway ; > ) If you have saved an old one (like I didn't) when you changed to a newer type and it is taking up space in your garage/shed/kitchen, I am the one to give you more storage space by relieving you of said item. I only need the sensor but will gladly take the who fixture and recycle the leftovers for you.