Try this place,
Dynalene, this is where we purchase all of our glycol. I believe we pay about $9.00 or $10.00 per gallon- somewhere around $500.00 to $550.00 per drum, plus a deposit on the drum. Specify that you want USP Grade Propylene Glycol. They use an inhibitor package that provides a pH level consistent with equipment manufacturer's recommendations – and it protects against bioactivity and corrosion. Plus, I think they even have free shipping.