Nissan 370Z Parts, Accessories, Performance and Tuning Products - by 370Ztuner.com
If you go to that link, you will see the banner is a nismo with canards and an adjustable splitter. It is sooo hot I oogle it all the time, no homo. As a rule for canards, I would reach for APR because they make high quality carbon fiber pieces. However, I do not believe they are vehicle specific, so it may be a shot in the dark. That being said, stillen makes canards that are urethane that will not fit the nismo directly, but can be easily molded with heat. Of course this is why you get so many complaints about saggy stillen lips and fascias
All in all, just google "370z canards the370z.com" and you will get several entries about canards for our cars. However, this is the only one about nismo's I could find because i too wondered about putting canards on a nismo, even though I have no nismo
canards
Stillen is probably your best bet, but ask your local body/custom shop, they may be able to steer you in the right direction. Good luck!