After hours of explaining exactly why this was so important, my wife agreed that I should do it. Well, actually, that didn't happen. I explained it to her, and she looked at me like I have two heads, and quietly accepted that I was going to do it anyway.
This is a preliminary build of the cylinder, just as a proof-of-concept. I built it to be able to be disassembled (nothing is permanently glued). I had thought that this might make the final product weaker, but it turned out to be stronger than I had anticipated. I may end up using this method to build the final one that matches the size requirements, so that I can re-use as many of the parts as possible if the need arises.
For this build, there are a few parts that are must-haves, but everything else was cobbled together from what I had kicking around in the garage. Feel free to modify, substitute, and improvise if you're going to build one yourself.