You can buy it, of course, but if you happen to have some comb, you can melt it down yourself and be sure it is pure. I found some sensible, step-by-step instructions here. You need a couple big pots, some screening, a waxed carton and knee-high nylons. Plus a bungie cord for securing the screen and something to stir with. Do not use pots or a spoon that you ever intend to use for cooking again. I got some super-cheap pots at Big Lots and used a gardening stake for a stirrer.
First you add water to the comb. You want a goodly proportion of water to comb, but not so much that there's any risk of the pot bubbling over and covering your stove with wax. I'm pretty sure that would be a really bad thing.
I did not have an assistant to photograph the pouring, so you'll just have to imagine it. When I was done, I had this:
A pot of wax suspended in water and a pile of slumgum.
Yes, slumgum. Isn't that a great word? It's all the detritus from the comb that isn't wax. You don't want to think too hard about that. If you are processing mostly honeycomb, you will not get a lot of it.
It still has some wax in it, so it makes a good firestarter. I made slumgum patties (briquettes?) using a cut-up paper towel roll – my own invention, thank you very much.
And I should issue a warning here: Beeswax is highly inflammable. NEVER LEAVE MELTING WAX UNATTENDED.
Voilà! Pure, organic beeswax.
It smells really nice, and should be enough for my needs. You'll notice that there's not a lot of it. Yes, rendering that entire log full of comb yielded just this much wax (and a whole lot of slumgum). It's amazing how bees have evolved to produce this stuff and use it so efficiently.