Go chemical or hypergolic
Some phosphorus sealed until needed perhaps or sodium and water
Something like potassium permanganate and ethylene glycol, peroxide or something similar. Mix as required, and add some iron oxide and aluminium powder for good measure.
Not sure of the min ambient temps at which these occur might need a slightly friskier combination at high altitude temps
Hydrazine and an oxidiser?
ammonium nitrate, ammonium chloride, zinc dust and water perhaps?