Build a Lightsaber

Hey folks, in preparation for an upcoming Star Wars larp in my area, I've been doing some research, goofing off, and asking around for ideas on how to build a functional, durable, light-up saber that is larp safe.

In this particular instance that means enough foam on all striking surfaces that you can't feel the core beneath. I've already (with some help, of course) come up with the majority of the things we'll need but I'm running into some difficulty with finding a foam that is dense enough, thick enough, and diffuses enough light to allow for the construction of one of these bad boys.

If anyone has any leads on foam roughly in the 2lb density range, or something similar to traditional boffer pipe insulating foam in white or any possible alternatives for creating this monstrosity, that'd be rad!

Of course, if this pans out, I'll feed you guys some details and results.

Thanks for reading, hopefully someone out there has some brilliant ideas!