I haven't seen other materials either for this one. However, you could look at replacing the handle and/or scabbard with a different material. Like Sir Didymous said, I'd probably shoot for replacing the scabbard first since there's no reason for it to have that much weight to it and it's easier to replace it than it would be the handle itself. You should be able to find a cheap leather one for $5-10.

Another option might be to attach a strap to the scabbard to give it extra staying power, though that may or may not work depending on the shape of your calves and where you wear it; the strap may simply slide down your leg regardless.