What I finally landed on was an ignition system that uses model rocket igniters, gun powder, and magnesium to light the thermite. The model rocket igniter can be set off from the 12v line inside your computer. However, it isn’t hot enough to light magnesium shavings, much less thermite. To get it to work, I needed to add some gunpowder. A small amount of gun powder would get hot enough to light the magnesium shavings, which in turn were hot enough to light the thermite. I had to be careful though, because too much gunpowder would cause a rapid expansion, blowing the thermite everywhere instead of lighting it. You can actually see some red thermite being blown out of the external hard drive and the laptop as the gunpowder ignites.