If a series of sixty 2 volt chip LEDs were soldered together in a strip with no wire between them, (thirty running up one side of the light saber and thirty running down the other side, back-to-back, facing two directions with an insulating strip between them) they could be connected to a bank of thirteen 9 volt batteries, no driver required. (2 x 60 = 120 volts; 120 divided by 9 = 13.3∞)
120 volts also happens to be the standard household voltage, at least here in the USA, so it would be a simple matter to use a transformer and plug it into the wall socket. The transformer wouldn't get hot because you would already be drawing 120 volts, not actually 'transforming' the voltage for the LEDs at all.
If only someone out there could solder such tiny chip LEDs together like this; (they do come in RED for Vader) Then the strip could be inserted into a custom-made translucent saber-shaped tube with a rounded tip, and filled with pigmented resin.
I think we would finally have our super-bright light saber, brilliantly lit from end to end.
Any soldering heroes out there with good eyesight?