5 years ago I was in Berlin for a school trip approximately at that period of the year and couldn't imagine not orienteering for a week, so I contacted the club
TOLF Berlin. I keep an extraordinary memory of it - travelling several evenings in the week to the very eastern part of the city and training with them. The website doesn't seem to have a contact form, but you could try to write to Bernd Wollenberg, elch@tolf.de (hope the e-mail is still valid). This was the very active trainer who organized everything for me. Note however that I suspect most people are likely to be on holidays, at WMOC, at WOC or O-Ringen... But in the worst case, there are always maps :)