I added some 'Long 3 bight turks head' knots to these key chain carabiners. If you're looking for some smaller diameter cord like I've used here(got mine off ebay), try contacting R&W Rope Warehouse((800) 260-8599), call and tell 'em what you're looking for since they're not set up to sell online. The 'Handy Hundred' cord looks like a good candidate for knot work, though I've not tried it myself. And with some 1/16" glow-in-the-dark cord from CoolGlowStuff.com.
