Municipality of Drage (Samtgemeinde* Elbmarsch / Harburg county
/ Lower Saxony).
Its ratio is 3:5. It's a green over white horizontal bicolour with
the coat of arms in the centre of the flag.
Description of coat of arms: The shield shows a black draw-well in
a silver (=white) field.
Source: I spotted this flag on 29 March 2007 opposite to the bureau
of municipal affairs in Drage. The image of flag matches the description
given in http://kommunalflaggen.de/.
The flag was submitted on 7 January 1991 at Hauptstaatsarchiv Hannover.
*A "Samtgemeinde", also called "collective municipality"
is a combination of several municipalities to an administrative community
in Lower Saxony.
Klaus-Michael Schneider, 8 Apr 2007