Not published Andy, but a couple of nice on-line resources worth visiting:
CockpitInstruments.de
Aero Part Identify Board
With regards books, "Cockpits deutscher Flugzeuge" by Peter W Cohausz [Aviatic Verlag, 2000] or the Schiffer translation of the same volume does include Geratenummer Fl-numbers for a majority of the major types used by the Luftwaffe...
Cheers
Peter D Evans
LEMB Administrator