There are any number of small transformers that will give you a spike with lots of volts if you have a sharp enough spike on the input. I have seen fence charger circuits that would work with a wall wart transformer. You could just use a small relay, picked through the N/C points (basically a buzzer) to give you the pulses. I wouldn't fool with that since a multivibrator circuit is so trivial to build, particularly if you just want it to go, without caring much about frequency stability.
