The Voynich Ninja

Marco and I are currently trying to fill out some holes in the map. Some of the areas that are missing are the north-east and north-west of Germany. So we are looking for 15th century charters (Urkunden) or similar documents from cities like:

West: Bonn, Cologne, Düsseldorf, Essen, Aachen, Trier...
East: Anything around Berlin and to its north

Any 15th century documents made in these regions will do, the more the better. You will be credited.