Then DAMN they are hard to find, i have only ever seen 1 set for sale and from memory they were close to $800 used..
Buyers guide for a V35.. there's a big list. I think most of it is really common sense when buying a vehicle.
Things like making sure the car is in perfect or near perfect mechanical condition, making sure the body and paintwork has no blemishes, ensuring everything inside the vehicle works, finding the right amount of km's for the right price... etc