Not sure if that would be big enough. Its a bloody big lista cabinetYou can buy those electrical panel heaters from RS and the like I put a small one inside my old temperamental TIG set.
Wouldn’t last one night in my workshopSilica gel bags would be cheaper then you have to dry them and put back again
I’ll have to have a quick measure of the gap under the bottom drawer as that tube is 81mm in diameter apparentlyI bought a 25W version of this a few years ago (couldn't quickly find the exact model on screwfix). It's only 40cm long and has been very reliable.
Dimplex ECOT1FT Wall-Mounted Tubular Heater 40W 408 x 81mm | Heaters | Screwfix.com
Yeah - mine sat at the back of the dehumidifier over the winter to stop condensate freezing. It would regularly get dripped on and didn't seem to suffer.I’ve just ordered two heaters from screwfix. Due to be delivered Wednesday.
Not too worried about low voltage, the heater won’t get damaged inside the bottom of the toolbox, and it appears to be plastic so likely double insulated.