Trainworx put out a set of "Bicentennial" models which included two tractor trailers and one PS2CD 4427 3-Bay covered hopper. They sold out overnight. I could not find any information on the Trainworx website. TopHobbyTrains looks like they still have the hopper in stock. And possibly the tractor-trailers too. The unmentionable hobby shop is sold out. The link to TopHobby is here. The Fedex tractor cabs and trailers are also selling VERY fast. If you like N Scale vehicles, these models from Trainworx are very high quality and seemingly very popular. All are listed on TroveStar's Trainworx section which now details 1251 different products from this manufacturer.
How thoroughly did you search? Here's the product info flyer on the Trainworx site: http://train-worx.com/16-6bicentennial.gif
Also, though I didn't see them listed, I would hazard a guess that TopHobby can get some of the new Fedex cabs and trailers as well. Their service is excellent to boot!
It probably wouldn't be as finely detailed if it was motorized. Being such a limited run doesn't help with the cost anyways.