There are also those 3/8" diameter white fiberglass rods that are sold as garden stakes. I use one on the rear window and two on the "upstairs" windows
. The other, shorter ones are clear plastic rods (tubes) that I salvaged from some domestic project. They are not as stiff as the fiberglass, but they make do. Their ends are plugged with short 1/4 - 20 pan head bolts that are glued in place so the rods do not slide through the rod supports. No more metal rods that bend at the slightest touch.