It appears "Glenn" just became a new member to finish his piece then left. He's most likely not responding because as many do, they feel if they don't share any information it makes their prop more valuable.
However, Glenn if you come back please accept my apologies.
Regardless, put me on the list of folks who are interested on making their own.
Yup, they're called "Tofflemire Matrix Bands Retainer" [among other things].
There's the handle too, which I think is a some brand of "Dental Octagon Examination Handle". The new version of these can be picked up for cheap.
Wanna know more ? Here are some pics of the model that a friend found online. (French Craiglist).
It is, indeed a mini gas welder as you can see on the attached images.
I'm currently working on a 3D model of it with, obviously, real references.
I'll keep you posed on this project !