duddly has several high quality model cars. I know some other modelers here also have cars. Turbosquid.com is a place where you can find what you want but the price is astronomical. Look for cars in the market place then contact the merchant and see if they have any other vehicles available. DAZ3d.com also has some cars. You may get this question answered faster in the Rhino, Softimage, modeling, and amapi forums.