I was just talking to a friend who sews a lot, and she said Coats & Clarks Upholstery Thread is probably what you want. It's 100% nylon, 3-ply, and since it's UV-resistant, it's often used for sewing outdoor gear. She said there's at least 100 yds on a spool, and it's very tough stuff.

She also said the T26 probably is the color number.

It should be available in most sewing shops, but may not be exactly with the regular sewing thread, so look around (and if that fails, well..... ASK.) <img src="/images/graemlins/smirk.gif" alt="" />