@AJ You are in the right sort of place, I have another of these bezels in my workshop here but I, like you, cannot find one anywhere on the web :-/ I looked again at the jack plug socket it came from, it is is fact a3.5mm dia not 1/4 as stated above.
The basics are though that it is a plastic washer, 4mm thick with a 6mm hole that is counterbored 8.8mm dia to half way through.
There's probably lots of different parts, grommets, washers etc. that would work. A well-stocked hardware store with lots of bins of the "fiddly parts" for various things would probably turn something up.
I realized that with that plastic disk, you could very easily scribe reference marks onto the disk and the flashlight host's bezel for different pre-measured focus distances. That would make impromptu burning and balloon popping demonstrations run very smoothly!
@ AJ...Hmmm, that is a great idea, I may look at marking mine...I have found that around 2.5 turns gets you from infinity down to closeup. Burning distance seems to be within 1 turn. I have not tried a balloon yet so have no idea how far away that can be done......I will have to try it sometime *Thinks I am running birthday parties this w/e, I will take the burner along with me just in case *