I have seen them sold as a set on the internet several places.
Here is one:
http://infinitipa.zoovy.com/
EverythingG35 web site
Page 3 of factory accessories
$66

2003 TwBlue 5AT Sedan, sunroof,
Graphite Leather, splashguards, HKS muffler,
14 wire Grounding kit, 350Z duct, Stillen HF/AB
Underbody rear diffusers, Drilled alum pedals

Thanks. I'll have to get a pair. I also saw that everythingg35.com also has the Z tube and Stillen high-flow airbox. . .everything I need. I like that, one-stop shopping.

Counting down the days for G35 #2.

<font color=red>2003.5 Garnet Fire/Graphite G35 6MT Sedan</font color=red> - R.I.P.
Premium Package • Navigation • Winter Package • Aero Package • 350Z intake duct • Stillen high-flow airbox