That's upholstery thread. Just call around to your local upholstery shops, either the stores that supply the materials or the people who actually do upholstering.

Ask if they carry #69 black nylon upholstery thread in small amounts. "Small amounts" in the trade may be a 4-oz cone. That would keep you busy for years. <img src="/images/graemlins/grin.gif" alt="" />

If a working upholstery shop says they have it, but only on a large cone (very large), ask if they would sell you some, either by length or weight. Two ounces is a lot.