3d warehouse has a ton of Prius models... of course you'll need to convert them to obj to be useful, but other than that' they are free. Easiest way to convert is to download the demo of the pro version of Sketchup which will allow you to convert to OBJ.

http://sketchup.google.com/3dwarehouse/search?q=prius&styp=m&btnG=Search

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