This script will create a knot from just about any ribbon you provide. As long as the ribbon is about 75 x 500 pixels, it will work. To make the knot look even more realistic, make the ribbon 2000 pixels long. That way, the script will be able to use the whole lenght and the pieces will be places as if they were one single ribbon. That will allow you to use a ribbon with a directional pattern, a wide gradient, etc. Since all the pieces are actually placed as if they came from the ribbon, you can also use a translucent or cutout ribbon and you will see through it, as you would normally.
And if you want to attach this knot to something else, like a tag, or around the stems of flowers, you can also do it since the layers are left unmerged (but grouped so they wont get disaligned if you move them).
You can get this at my stores: Creation Cassel, Do It Digi, Scrapping Whispers.
And if you want a chance to get this script for free, just check out this thread at DST and add your name before Monday night.