Windlace?
I think you're looking for windlace, although I've never seen it without some sort of texture (check the attached link). If the original welting has shrunk, try re-stretching it with a heat gun. I had good results doing this on an EC127 several years ago.
http://www.calmuscleparts.com/store/PINCH-ON-VINYL-WINDLACE-C667.aspx
Retro Redo
Retro Redo found a source, but I wonder if Lloyd would give it up. Might endanger his business. 😉 But if you're doing just a couple of chairs perhaps he would sell you a couple lengths of it. Never hurts to ask. Just Google the above company name and you should find it.
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