They are a small I beam type rail. They come in eight foot lengths and will need to be cut to length and formed (bent over your knee) to the right curvature. You will need the wall stand off fasteners to hold it up in place and also a couple packages of the roller eyes that work with the hooks in the curtain/drapes. All those items are standard and available on line, on E Bay, and almost any RV dealer store.
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."