So many of you have asked about the organza-edged elastic that I felt the need to talk about it some more! Here is a close-up photo of it used as a sleeve finish on another garment. I believe I bought this particular one at MJ Trims in NYC a couple of years ago but I’m not 100% positive. It’s a very pretty and super-simple way to finish a neckline. Just serge it on, turn in and topstitch.
I did a quick search on Ebay for “organza elastic” and came up with quite a few auctions for it: Ebay auctions so it’s readily available. You might also do a search for “ruffled elastic”.