Alternatively, assuming that they are polyurethane boots you could just use a hot water bottle and strap it to the front of the boots with a bungee cord. I do this when there isn’t time to use my heated boot bag to get my boots soft enough to get them on. Fix the hot water bottle to the front of your
Boots before breakfast and they should be warm enough by the time you are ready to go skiing.
Maybe there’s new digital transformers that are light. If not you’re looking at 2lbs at least.
I just use the Snaptronic. Has a 220/120 switch. All you need is the plug adapter. (Swiss is different than France)
Edit- seems it’s now unavailable. You could get a 220v Thermic boot dryer that’s the same thing. Why they couldn’t put the switch in like Snapdry did is beyond me.