I was in the local Walgreen's store last week and was quite surprised to see they had a new 36" plotter in the photo Dept. Apparently they make posters to order now. Roll paper was right there and loaded. Lady said that all their store have them now. Doubt they have the range of software support that a Kinko's would...such as if your file is AutoCAD, then go to kinko's. But if you can shoot it out to JPG, TIF, or some common format, then Walgreen's could make it for you. A 36x84 inch plot would cover a larger tandem design if needed.
/K