There is a maker of wood plywood tubes up to about 4" or 5". Thier name is indeed Hollowood adn they make hollow tubes and rods. I got some from Woodworker`s Supply when I made my 200" refractor for the eyepiece tube stock. It`s 1/8" or so 3 ply plywood and the outer layer is a fair choice of hardwoods. Hollowood is at POBOX 1149 Clinton Township MI.48036-1149 and a phone # of 810-465-2737 Fax # of 810-465-6032. The tubes are available in some different lengths (I got the 4` length when I bought mine.
The present Woodworker`s Supply doesn`t have the items listed in thier catalog that I get so you may not be in luck there anymore.
Good luck with getting the tubes. I feel that I was very lucky to get mine.