This one is close to Cologne:
N5274A - Beautiful Cessna 172 SP for rent in Cologne / Germany
There is a big list of N-regs in Germany here:
N-Flugzeuge
It may not be up to date but worth a look I woould guess.
If calling from outside Germany, use the country code 49 and drop the first zero of the numbers shown.
Hope this helps
Be prepared, flying in Germany (and most of the rest of Europe) is not as cheap and straight forward as in the States. Get a thorough check-out in any case.