Allen VK6XL sends in this report:
An Australian on-line supplier of Aluminium tubing is:
Thicknesses aren't given, but outside diameters are; 1.59mm, 2.38mm, 3.18mm, 3.97mm, 4.76mm, 5.55mm, 6.35mm, 7.14mm.
All tubing lengths are 300mm. It is unclear if they are extruded or seamed sections, or if they are telescopic.
More description from VK6XL after receipt of his current order.