Thanks for the info Gameswat. I'm familiar with the American machines, a sort of cross between a Palmistry and a Green Ray, but didn't know they had blowers (presumably operating at fairly high pressure)? I have a Wizard's Pen down at Brighton, on loan from another operator (currently not working). That just has a red lightbulb shining through the holes in the plate. When I get a chance, I'll check to see if there is any evidence that there was ever a blower in there.
For ease of construction, I was going to go down the lightbulb route, although I've dragged myself into the 21st Century by using six LED strips running off a 3 channel chaser to give a 'scanning' effect. I'll give it some thought, and see if I can also incorporate some sort of blower - although to be honest, I need to keep it as simple as possible, and get it finished as soon as possible!