I'm assuming you're using a program other than magos for 3D modeling. If not, this is all gonna sound like gibberish.
Well, what you're going to want to do is apply a gradient texture to the light beam.
textures\grad2b.blp is a good one.
Then you'll want to UV map the texture on the beam geoset so that it looks kinda like this:
The shape of the wrap is already correct, you just need to scale it up and center the whole thing.
With some tweaking in magos it should look something like this:
[IMG]
Experiment with different effects and color, textures and what-not to get the best results.