I was recently looking for a lifeguard reach pole for my new lake association beach safety board. Minimal official lifeguard reach poles start at $60 and go up to to nearly $200. But at Ollies, in the mop and broom section, I found a 12' extension pole for $15. Threaded end is meant for painting ceilings or whatever, I guess. I attached a colorful rope loop and hung it on the safety board at the beach. Fiberglass with an aluminum telescoping extension, very stiff and lightweight. I bet it would work great for poling a boat. If you have an Ollies nearby, check it out. "Good stuff cheap".
I have an expandable aluminum pool cleaning pole with a friction adjuster. I would never trust it to hold under the pressure exerted while poling. if the friction sleeve were to slip while poling hard the result could (and probably would) be catastrophic!
I found one online that uses a spring loaded pin/button that sticks thru the outer pipe , like some collapsible tent poles . HA HAH HA when I get comfortable "standing" up I'll report
The telescopic pole? Just don't. You can only climb hand over hand. They are not balanced. The fibreglass part won't take levering on a gunnel. For $15... you can try it and no loss if you aren't happy. Remember though, these are designed for a very light load job and not for body weight pushing a canoe. Wear light work gloves in case the fibreglass splinters.
I made a pole from a piece of cedar lumber. Then I added a bell reducer (plumbing fitting) to the end for a shoe to protect the end and add some weight. The cedar was light and had a little flex. A collapsible pole is a terrible idea because sometimes you have to push hard on the pole. After I made the pole I used it on my powerboat to good effect when pushing off shallow beaches.