Real rear fog light at this site:
Nissan 370Z Lamps / Lighting
and I'm trying to tap in to the parking light with the standard harness wires on the right side of the rear fog light housing. Also check out this site for more info:
DIY:REAR Fog Light install with New harness for US spec 370Z + Radar hardwire w/pics
I need to find out which color wire to use. You can see the main harness junction in the trunk. I'll post my finding in a week or two.