You know those envelopes that Federal Express uses for small shipments? Not the stiff cardboard ones, but the soft ones made out of paper that is just about impossible to tear?

Is it possible to buy that paper in letter size or legal size sheets, in small quantities (say 100 pages)?

I am the promoter of the annual Death Ride, a mountain bike race for true lunatics that involves wading (with your bike) through a swamp that can run as much as chin-deep if you don't bypass the deeper holes (like here) and the numbers I made up out of light card stock simply didn't hold up. I'm looking for something more durable that I can print on using a laser printer.

Any ideas?

tanstaafl.