I have to concede, the gas tank in Han's belt is an exact match for the Nitrous Oxide from the Archer microflame torch used by the jawas, not a soda one. Lonepigeon was right, I have a real torch here and the can is spot on.
I thought it was the Microflame piece years ago, but it is ABSOLUTELY a soda charge on Han's belt. Made by Sparklets. I bought a box of them a long time ago and sold off my spares.
Sorry I missed this thread until now. I'm not on here much.
I did know about the Sparklets soda siphon top and bulb holder used on the breathing canister.
I'm pretty certain the exact scuba mask strap is from a vintage Mares Ventosa mask (the box for which can be seen in behind the scenes prop workshop pics).
I looked into soda siphon levers for the Luke ROTJ V2 and never found a match.
I think someone already mentioned above that the sparklets siphon tops (two white ones) were also used on 2-1B's medical computer stand too.