20-25 , yazoomills, going to be tough to find a decent tube from a local place, they tend to be not very good for mailing regardless of what the place will tell you. Most dont make it in 1 piece through the postal system.
Agreed PVC is the route to go on something that big, just use a heavy duty strapping tape or duct tape when sealing the end or the ends will pop off. There is some flex to the pvc, probably 25% of the stuff i get shipped in it has an end missing.