I just went and looked at a spare Origo up in my barn, to visualize how the neoprene would be inserted. This stove
came with a boat that I haven't had time to work on yet.
To my surprise, there was a neoprene disk on the burner! It fits over the circular wick area with the screen top, and under the metal disk that swings back and forth with the flame size control knob. It's just big enough to cover the first raised ring stamped into the housing of the alcohol cannister.
I think it's a great idea, and would not know about it without this discussion. By eye the neoprene is around a 1/16 of an inch thick. OK, for the sake of accuracy I just went back and measured the thickness. It is 1/16th of an inch, perhaps a (red) hair over. A bit hard to be accurate as it is very soft and the caliper jaws compress it.
This softness is what distinguishes it from inner tube, more than the thickness. Soft enough to conform easily to the gap, without deforming the metal. I'm definitely going to put one on the boat that is in the water, to at least use when leaving the boat.
Thank you to those who brought it up in this discussion.