For PG, look for a local "compounding" pharmacy, they will have it in stock.(Here it was Shavers Pharmacy) Wallgreens pharmacy will order it for you (usualy).
For VG localy, Walmart, health food stores, and some craft stores will carry Wiltons glycerine USP. Its used to keep cake and brownies moist. Should be in the same place that the Loranns flavoring is. It can also sometimes be found by the medicated lotions by the pharmacy in Walmart.
The most important thing is that it says USP grade.
It should be rated at between 99.5%-99.8% pure. (nothing is 100%pure.)
Some have found it for sale at tractor supply stores.
Regaurdless of where you find it, it should be as clear as water. If its even slightly cloudy, I'd find a different source.
Hope this helps