Take one cheap headband, and some ribbon slightly wider than said cheap headband.
I’m going to be putting a bow on the side, so that’s where I’m going to do my join. So, you’ll need to measure how much ribbon (doubled) is needed to cover the headband.
Stitch right up next to the each edge of the ribbon, making a little casing. I folded the ribbon in half so the nice folded edge will be at the ends of the headband.
Now you’ve got a covered headband, but there is still an unsightly join to deal with. You can cover it with a big flower, a bow, or just wrap it with a ribbon.
I stitched down the bow, and then used the center “knot” to wrap completely around the headband and hide the join on the inside as well.
And here it is, modeled by one of the people who happened to be in my sewing room today. Thanks, Michelle!