It's Feast Watson Black Hard Wax from Hammerbarn (Big Green Shed), it's a carnauba based protective hard wearing wax primarily for furniture.
Now that you've mentioned the shellac/lacquer method that sounds like something worth trying though, as I know the wax finish alone won't be protective enough in the long run.
In my previous post I should have mentioned that you will need to remove as much of the wax off the headstock as you can before applying the shellac. I think the shellac will go over some residual wax ok, but probably not a thick layer of it.

My preferred finish for necks is satin polyurethane (from the BSG) I used to spray acrylic lacquer but have grown to dislike the feel.
If you do want lacquer, and don't have spray equipment, you can get acrylic lacquer in rattle cans from SuperCheap Auto. They're pretty much everywhere AFAIK. Septone is a good brand, an dI've heard good things about the SCA brand but never used it myself.