...or something similar that's really strong, really thin and won't stretch?
I can see what you mean. I did pick some up yesterday and for what I am using it for, it's working but it does break pretty easy. I'm sure I will end up replacing it before Halloween.The picture hanging wire is not designed for any kind of motion. It's only good in a static use like a picture hanging on the wall.
I've tried it a couple of times for things and it just breaks after a few bends... I can pretty much guarantee this will not work and is not worth trying...