Another couple of options:
1. Get a hold of some Siccatite Skymetal, more specifically the hot kind, a dagger of which will cost 1002gp. Every round it deals 1 point of fire damage and "Hot siccatite can eventually ignite objects." Ignition temperature for wood is approximately 220 degrees Fahrenheit, turning water into steam is 216 degrees Fahrenheit. Multiply by a few daggers and instant steam powered nuclear reactor. Bonus use the the cold siccatite to cool it for more efficiency. (This method can be used with other heat engines, such as a Stirling engine.)
2. On the simple battery side Ultimate Equipment alchemical weapons section has both acid and alkali flasks, but the real fun one is bottled lightning at 40gp.
3. Where does the power come for an automatic resetting mechanical trap? 1500gp multiplied by the CR.
