Hi PhiLiSoPhik and welcome to ECF! I
buy my VG and PG from Shoppers Drug Mart. It must be USP grade and theirs is. They typically have small bottles in the first aid section. I ask for bigger ones to be ordered for me. If they ask what you're using it for tell them making essential oils. I believe you can get PG from tractor supply shops real cheap, but I've never done that.