Using a bug-zapper seems unnecessarily complicated. This is a moderate-powered stun-gun for about $5 bucks, less if you have the stuff laying around. The first time I got one of these, I took it apart, and put a new capacitor in it, at about 3 times the size.
Bug zapper uses oscillator circuit that converts dc into pulses tht goes to snall transfomer and the output of tranformer charges a small capacitor with 1KV voltage. These capacitor output is fed to net. 1000volts is the voltage rating.