Good luck! You are basically looking for a needle in a hay stack. According to this website there were only 25 Persimmon GM compared to 1031 Black GM.
Nissan 370Z Production Statistics
Like Isteve said, you are probably better off negotiating with the dealer. We have a local member who had the dealer put in customer Persimmon interior in his MB. It looks just as good if not better than the OEM seats, not to mention the dealer threw them in to make the sale happen.