I have a workroom for custom window treatments and there is a clear plastic tubing that you can get, I'm sure most anywhere, that is about as round as an ink pen. We use it in the rod pockets for sunburst window treatments. It is sturdy but has some give, so you can arch it in half cirle windows. I brace it at the bottoms and if it is a larger window I use a small hook at the top of the window as a stablizer. ( such a small coffee cup hook) If none of your fabric stores carry it, I'm sure they could order it. Or you might even try a hardware store to find something similar. I hope this helps you.