I've got the exact same bass, and have the detuner on it. I got it at
http://www.bestbassgear.com/ . Sometimes the selection varies, but you should be able to get one that matches exactly.
If you get one, i recommend using some loctite on the screw when you install it. The detuner screw isn't very deep, and it can loosen up after a while. If you're using it alot, you could have trouble with the screw loosening. I've used loctite on mine, the one designed for bolts, and its held just fine. I really recommed using some kind of bolt glue though, as you don't really want to have problems with it at a gig.