Hm, cool idea. I wonder if "awning" (is this the correct term?) of the 3233 police car could be customized for this purpose (using two, separating the ends to enlarge in length) ... ![Huh? ???](http://www.playmofriends.com/forum/Smileys/classic/huh.gif)
... and then sprayed in THW-blue.
Hello Jochen, the technical term is a tilt, although awning is more commonly used and seems always to be used in relation to ships or boats. Lots of people may not understand "tilt" used in this way - I certainly didn't when I first came across it! "Cover" is a possible word, too.
I wondered about the cover from the earlier Playmobil trucks, too, but never having seen one in real life or for sale, I didn't take it further.
I've had some spray paint made up to RAL 5002 at the local branch of Halfords, a motor accessory and cycle chain of shops. My next custom just needs a bit more painting and it will be ready to show. Over here, RAL 5002 is described as ultramarine blue rather than "king's" blue.