http://www.stockinteriors.com/AutoCarpe ... odelId=320
Starts at $270, and you can pick just about any color you want. The link above is for the entire truck, but they also sell the passenger and cargo areas separately.
I used these guys a long time ago for my Frontier. Fitment was good, but my carpet cutting skills needed improvement back then (probably still do today, lol). Suffice to say, you may need to cut some of your own holes, or minor trimming. Overall, though, the results were good. I think the carpet has held up well, but I haven't taken a good look at it recently.