Haven't read the whole thread, but I bet you could make a spring loaded candle holder with a spring and some plumbing supplies i.e copper pipe and end cap etc.
I can't see any reason why not. I've been burning home made pure beeswax candles in my spring loaded holders without any problems.
The main downside is the holders can be picked up cheaply, for a couple of pounds. If I made my own the spring might cost more than that.
The whole point of my original post was to see if there's something ready made for sale somewhere. With all the self sufficient, prepping, off grid type shops I'm still surprised there's not something.
Still, interesting to see what everyone has.