Okay...now this is something I'm recalling from vague memory - so you might wanna check up on me. This was also for neon tubing...so with mixed gasses it might be different.
To find the correct operating voltage for the tube (assuming you're using a traditional transformer type ballast and not an electronic one), connect it up to a variac, and strike the discharge. Then decrease the voltage to the point where it's just starting to flicker. That's then 78% of the correct operating voltage.
Then you just need to find a ballast rated to that sort of voltage/current. Though it's a relatively small tube - so voltage probably isn't a huge problem...current limiting is, and I really don't know how to go about finding the correct operating current. Maybe the simple one would be to stick a couple of incandescent bulbs in series with it - see how much that reduces the tube heating by (just using them as high power resistors).
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Another possibility. The small 12V inverters used to drive CCFLs (like those used by modders in computer cases and such), will happily drive small neon lamps and such - you might want to give each "element" a shot with an individual one of those.
This driver might also be worth a look.
BatNeon Driver for sale at LED Sales. You might have to email them to see if the open circuit voltage would be sufficient to strike it though.