Consider the sort of cold-cathode fluorescents that are used to backlight LCD displays:
These are available quite cheaply online - search for "cold cathode lamp". Often they come with inverters that run from 12V, so you can straightforwardly run them from batteries and avoid having the talent cabled to the mains. The tubes themselves are about 1/8" or 3mm in diameter but they're quite fragile on their own and usually supplied in a plastic sleeve about 3/8" or 10mm in diameter. They usually come in either 12 or 4 inch lengths.
The "white" is usually quite cool and cyanish, which may be good or bad for your application. They also come in red, green, blue, yellow and UV, among others. You could bunch them together and put the results inside a diffused tube (or a tube with diffusion gel) for a different diameter, more brightness, or mixed colours, etc.
I have a whole case full of these things with dimmable inverters and they are very handy.