Thanks for the link, totally missed that one.
In parallel (while i find a source of a plasma tube) im planning on simulating the lightning by doing the following
1. A frosted tube on the outside, let say i use a 1" thin wall blade tube and sand it... the idea is that its not transparent so you cant tell whats inside.
2. Make individual lightning bolts out of a translucent plastic (3d printed in shapeways of course) make several paterns that connect from end to end. on the end they would have a sleeve for an LED. Think of it as fiber optic nerves. I know that eventually each beam will not carry the light all the way trough but if i place the LED's in several spots and light them up at the right time it might work.
3. LED's everywhere and make a customized controller for them... a simple LED random sequencer at high speeds. This will not be controlled by the soundboard because it would be too much to handle.
So its tricky but doable... not as good looking as a plasma tube but good enough to impress a few kids.