You're giving me too much credit. I just threw a bunch of money at the problem.
I know that most terpene and essential oil products are sourced from natural "food" and food-like sources, but I think the "grade" is important... particularly the levels and types of impurities present. For instance both D-Limonene and b-Myrcene are available in many grades, from technical to food to ACS / Reagent grades, and many below as well I'm sure. Seems anything higher than food grade is very expensive. Some websites selling "food grade" often seem confused or misinformed about what "food grade" means in technical terms and possibly have them mislabeled as "food grade".
https://www.youtube.com/watch?v=1TOGLx7K0Jw
That's how I do it to. Winterized BHO and 15-40-% PEG depending on strain. I use a magnetic stirrer to mix it up around 140 F, but can be done without one just using heat and a little stirring. People don't want to admit how easy this is, because it's damn popular! ;-)
The one problem I've ran into as that on some strains, no matter how much care I take to fully winterize there are little solids that the PEG won't dissolve...dissolve a crystal clear slab into peg and it will reveal any waxes or buddery solids IME. Been having some trouble with this currently actually...
You mean the actual pens? If searching ebay try "bud touch" or "open vape"
I get mine on DHgate from the seller "healthyvapors" http://www.dhgate.com/store/16926885