Thanks a lot for all this information it's just what I'm looking for.
I was at my local Lowes yesterday, and was in the garden department, and I saw something that made me think of your request...
Basically - in the gardening department - near the trellises and tree support area, there was a display with a rack of various "support poles" for trees. They had ones made out of wood (pine I think - they were fairly lightweight, at about 20 x 20mm in cross-section, 1.2m long), plus bamboo rods - but they also had these long "poles" - about 15mm in diameter and made of fiberglass (I think), pointed at one end - 1.2 or 1.8m long. They were very inexpensive, too.