Bill,
I've never owned a whisker pole. For a makeshift solution, I have a nice wooden paddle. It's made from some very light-weight wood. I permanently keep a short bungee wrapped around the handle, with the two hooks sticking out. When I want to pole out the jib, I hook the clew cringle with one of the hooks and wedge the blade where the mast tabernacle would be if you have a deck stepped mast.
That solution has a certain minimalism that appeals to me, but also has the benefit of not cluttering up the boat with yet another special-purpose and difficult to stow item. (The paddle is needed anyway).
The way the jib sets with my arrangement is not ideal, but it came close enough that for many years I didn't feel like bothering with something more fancy. Recently, somebody gave me a spinnaker, and for that I needed a real pole. I made one myself, rather cheaply, and a whisker pole could be done the same way. You need to buy the
spinnaker pole fittings, they are not that expensive, and then use MarineTex to glue them into a tube of the desired length.
You could use aluminum, if you can get the right diameter. You'll need 1"ID for the standard "small" size fittings. As it happens, I used a piece of bamboo, which I selected so that it had an ID of approximately 1". I gave it a few coats of varnish for extra protection, and so far it's worked fine. Cost about 1/3 of a spinnaker pole kit (like the ones made by Forespar for dinghies). Ready-made, adjustable ones like you describe must be even more expensive.
I'm not a bamboo expert, but after seeing it used for scaffolding in Asia, and reading about bicycle frames made from it, I just had to try it. At 1" ID and about 1/8" wall thickness it resisted all my attempts to bend it, and seems lighter than an aluminum pole. If you have access to a good supplier, it would be great material, but any other strong and light-weight tubular material would do.