They also make a "beading transformer" -- a transformer that causes the light to make "beads"
like a string of pearls in the tube. [The beads are more like small blobs -- not true perfect
The transformer has an adjuster on it too so you can change the speed and direction of the flow of the beads [or make them stop altogether!] Neat!
These transformers work best with pure gas -- straight neon or straight argon [*no mercury* -- mercury has it's own frequency response, which interferes with the argon's response, so the beads are too broken up.]
Note: they sell European transformers too -- that take 240V/50Hz [USA is 110V/60Hz]
Here's a posting
by someone who says he has some uranium glass. He might have some for sale. Also, here's what it looks like pumped with argon/mercury.