Hi VORTIME,
try
www.pe-aviation.de
It´s a very small operation at Moenchengladbach Airfield (25km west of DUS) and you can get there by train and bus.
They have two Katanas (approx. 120€/h) and a PA28-181 (approx. 170€/h) for hire.
Very friendly staff, coffee and cake for free and cheaper than most other ops in the area...