U/S Cessna 172 (pref N)
Hi 2c,
If you haven't already you could try Paul Nalson aircraft salvage
http://www.nalsonaviation.com/
He has a massive stock of all sorts, from a wide variety of aircraft. I know we sent a 172 to him a couple of years ago but that was a Reims F172F so maybe slightly different to your model.
Good Luck