Alpine Model CD changer for stock head unit?
Autoclass (http://www.autoclass.net) sells the changers and necessary optical cables for around $400. These are the same actual Mercedes-Benz brand changers with the optical interface that the dealer sells for $800.
Another option is to use a CD changer with an RF modulator interface. If you're not using the ashtray, you can mount the controller box into the ashtray space. Or you could use the sunglasses tray underneath the head unit and drill a hole for the wire to run through.
Probably the best option is to replace your head unit with a high quality aftermarket head unit and aftermarket cd changer. Some head units will look nice in the stock location once you make a black plastic bevel to go around it. A good example is the Nakamichi CD-45z-a (Amber version). It's probably the highest quality audio for its price range and the changer would fit nicely in the glovebox.



