I designed a thing!
I tried my hand at designing something for 3D printing and it came back:
The color is a bit more fuchsia than my daughter was hoping for. She wanted a pale princess pink, and this is more of a '80s Raspberry Beret kind of pink.
The material is strong and pretty flexible. I haven't really stressed it to find out if it breaks, but it bends a bit and always returns to its original shape. The finish isn't totally smooth; it has kind of a velvety feel, but not at all fuzzy.
It took 14 days from the time I clicked "buy" on Shapeways until I was holding it in my hand (10 business days).
For wrapping up headphones, it totally does the trick, and it fits neatly into the pocket of my laptop bag.