I think this was an optional extra for the 2.8 model, if not here then in the states.
Your best place would be the main dealer or a breakers, breakers would not bother removing them though from the car so it would have to be a old school breakers so that you could remove them your self.
Personally I think it make the car look old and would not do it as you will probably find that they are fixed like the Avant's and will need the rear quarter cut out so that you can get to the rivets then have the window bonded back in (just removed ally ones out of an RS4 at the weekend).