I bought some of the nylon cord from Hancock Fabric too. I kept wishing I could find something that looked just a bit more similar to the original cord.
I decided to check the ribbon/lace/trim rack at Walmart, and they have some cord that looks very close to the original in size, color and texture.
I bought a yard or two, but I can't seem to locate it to take pics right now. I believe it was about 51 cents a yard.I will keep looking. If you can't find it, and my store still has it, I can send some to you.
If it were me, and I found the cord, I think I would take the cord out of two other dolls and put that with the LEs, so they would be fully authentic. I would put the replacement cord on some newer girls where it might not matter so much, but that is just me.