Please check out....
Nismo 370z body panels
I found a place that actually sells it for $1200 from an after market place for the whole kit. Check that thread for pictures.
Btw, Dealership should be able to order these Nismo body parts, but they would need a VIN of an actual Nismo 370z for record to order it as replacement. It all depends if they want to go through that kind of trouble for you as you're not really doing them any favor nor are they making any profit off of you.
They'd have more initiative to budge if you're making all this arragement prior buying a car from them, they'll promise you this and that, but they can also just say all this just to get you to buy the car but never follow through with the rest. They may make excuses and all kinds of b.s. later