Thermite wouldn't be too hard to, would it? Potassium permanganate and glycerine can be used to start the reaction among the metal shavings reliably with a small (~2 sec) delay.

It could be tough to manufacture the components if they aren't available. Magnesium is a more reliable way to ignite it.

Both of those are readily available at drug stores, I'd find magnesium ribbon a bit harder to get, honestly, though I don't know how that changes at commercial scale.

What do they have potassium permanganate for at the drug store? I didn't think they had it.

Sorry, that one is a fish tank cleaner, but still easily available.