A couple of things:
If anything else fails, you can probably find glycerin (glycerol) at your local supermarket or baking supplies store as glycerin is commonly used to make fondant icing, etc..
It is always good to make the distinction of "pure" when it comes to chemicals, and this applies to any and every chemical. In fact, glycerin is not the name of a chemical, glycerol is. Also, there is no such thing as a "pure" chemical, even the purest of chemicals always has impurities. Chemicals are manufactured in "grades", which means that a set of standards is used to ensure that they conform with certain regulations. it is important to have the word "grade" as reference. I always suggest that people use USP grade for cosmetics or food applications. Perhaps this link would help to understand what I mean with grades:
Glycerin Specifications, Crude Glycerin, Technical Grade Glycerin, USP Grade Glycerin
As you can see, the word glycerin, has not purity attached, the grade, determines the purity and no all "glycerins" are created equal. Low grade synthetic glycerin can contain, among other things, methanol. This link also explains why one may want to buy USP grade:
www.cleaning101.com/oleo/USPGlycerin.pdf
I hope that this brief explanations help to clarify the issue of purity in chemicals, particularly of glycerol.
Al raz.