2 brackets or corbels. I bought mine at Home Depot in the moulding section (ranging from about $5 – $10 each) but they also have them in the curtains section (with holes already) and I’ve seen salvaged corbels at several thrift stores before. Shop around. They just need to be thick enough to drill a large hole through for your rod.
Wood dowel slightly wider than your window. Mine is 1 1/2″ I think and cost about $1.50
Shelf same width as your dowel. We had ours in the garage from a closet project that never happened!
Do It And How 