That would be a "stick light" or "light stick" ballast. Lots of places to get them. fleaBay, theatrical lighting suppliers, fancy architectural lighting suppliers, Kino Flo dealers...
They're also pretty conceptually simple if you're the DIY type. The crux of the typical design is a fluorescent tube sleeve (like, say, any of the dozens Lee and Rosco sell) and a hardware store ballast. Kino's design instead uses external cords and leaves the bulb completely exposed, but it might be workable depending on your use.
My daughter got one of those in a birthday goodie bag: you bend it in the middle, and shake. The resulting glow is pretty, but not bright enough for studio use.
