I've found two products readily available in BC that one might not suspect to be denatured alcohol, but despite not having "denatured alcohol" written anywhere on the product, they are denatured alcohol.
BioFlame: 95.6% ethanol, and 4.40% ethyl acetate.
LV Lacquer Thinner: 91% ethanol, 4% butanol, %4 isopropanol.
I'm not a chemist (please step in if you ...
Methyl hydrate = methanol. Also called wood alcohol.
There is already methanol in most versions of denatured alcohol and in the general equivalent sold in the UK and elsewhere, and these are of course commonly used to dissolve shellac.
And while methanol is quite toxic it is completely volatile, i.e. all of it evaporates, so none remains in a dried shellac ...
Isopropyl Alcohol (IPA) seems to be fine for shellac and isn’t as toxic as methanol. It should be freely available anywhere - I got it from a high street chemist in the U.K. years ago, or get it from amazon etc.
Two additions to Grpahus's comprehensive answer:
Skin absorption of methanol is also an issue (chemistry.se), so gloves should be worn. Latex isn't much good; nitrile and PVC are not much better but for short-term use are recommended by some sources. 100% methanol is worse than 10% in ethanol, though how much worse is another question (and one for ...