Aqua Fortis is available from "Track of the Wolf", which is a blackpowder/reanactor company. They are at trackofthewolf.com. I have some sitting above my workbench. I'm just waiting for the project to come along. If you try going this route you may try a heat gun for a heat source. I would think you'd have a little better control. I've seen heated irons etc. also recommended. Which ever way you choose it should be worth the effort.
Frank