Hi Ryan Yu,
Just curious what you will be using the model 3 battery for? I didn't think there would be a market for the battery packs, at least this early in the model cycle.
Otherwise, your best bet will be see if any of the M3 cars that have had a very short life have a usable battery. I believe there have only been a handful of M3 involved in crashes that left them "totaled". Then again, those batteriesmay have been rendered dangerous, even in the scrap yard.
Best of luck in your search though.