Here you go:
http://www.courtesyparts.com/cabin-micr ... cPath=4700
You might not have one installed however it can be installed as per instructions above.
I decided to leave well enough alone.....one less maintenance item. Personally I think its a waste and another way for the manufacturers to make money. I had them in previous vehicles and I would occasionally get a musty smell. I've never had that issue with my Pathfinder's or other older vehicles.
You decide what is right for you.