Looking for cardboard or plastic shipping tubes.

I say this with tongue-in-cheek: I've seen these for sale 'off-the-shelf' in many store accross the USA. Source: Home Depot plumbing department. PVD drain pipe is pretty sturdy stuff. Cut to length and cap the ends. They usually come with a small radius, however unstable. Perhaps the radius for your purposes can be set and stabilized with some heat and a cable or rod then affixed to provide required stability, if needed? Maybe someone else can be of more help.

Am I off on this one, or is a 200" length with a 62" radius.... a circle? Who's gonna ship a 10' circle?

I think you are off on this one, the circumference of a 68" circle would be about 427", so he is looking for basically half of that or 200", which would be almost a half circle. It would take about a 16 1/2 foot section of pvc pipe and some heat to bend it. I think the drain pipe is too rigid and the wall too thin to make the radius for this bend on a 4 inch pipe, especially using heat, and it would take a lot, to bend, pvc will give off some toxic fumes when heated also. The simple solution would be to get some black ABS plastic, bellows type, flexible drain pipe from Home Depot, bend it to the radius desired and secure it with string or cable, kind of like an archer's bow and cap the ends. One question, what kind of drawings require 16 1/2 feet to store, and why must it be curved?

I just found some kraft paper tubes 4" diameter x 48" long and they come in a pkg of 5 for $20, if you don't need a smooth radius, you could use these with a coupling in between to get your required radius and length. I found them at www.mcmaster.com and searching for shipping tubes. You could also cut these tubes at an angle, twist one end 180 degrees, tape it back together, and begin to make your own radius, cut the sections short enough and you could get a pretty good bend. That is the way pipefitters do it anyway.