It should be simple , easy and have availability.
Search instructables for "Plasma speaker". You can generate an electric arc, AND listen to your music too!
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Use a disposable camera flash transformer to power a cockcroft walton voltage multiplier. You can easily get around 1/8inch arcs.
Car Battery and a couple of carbon rods.
I'm assuming you want to make a big sparkYou can pull apart a microwave. That link shows you how to do it and shows some arcs in a video.