Has anyone seen the new Lumisource plasma globes yet? They have one called "Blue Planet Electra" and another one that's cube-shaped like a Borg ship.
They're hand-blown glass with a very tiny amount of phosphor dusting the inside to brighten the surface arc and create more of a subtle surface glow inside the sphere.
In the planet Earth shaped one (made of blue glass), the blue phosphor is where the water on the globe would be, and the green on the land masses. But it's so thin the globe still appears transparent and the discharge inside isn't hidden.
There is also a purple glass cubical or diamond shaped one but I haven't seen it in action yet.
Very inexpensive too, under $30 at Radio Shack. I wanted to get one of each, but chose to get a UK Light Cannon instead so I could only buy one; the Blue Planet Electra version.