A full oem Nismo kit sells for like $5,700 at
Z-1 Motorsports. It's going to be at least $2K for the wing +shipping +paint.
To be honest, I think the Seibon wing looks better. To each his own, but I can think of better ways to spend that much. I haven't seen too many Nismo owners wanting to remove that wing. I wouldn't want to if I had one. Good luck with the search.