The first thing I'd do is see if Nissan will still supply a new one, and what that would cost.
Call Greg Vogel at G-Spec to find that out.
www.gspec.com
If used works for you, then I would next try
www.car-part.com to see if there was one local at a salvage yard.
I would imagine the 4-door carpet is identical to the 2-door carpet? Manual transmission carpets might be different?