Here's what I "created" for our cabover bed (where I liked to take refuge when Hubby was snoring)
I bought a twin-sized flannel sheet set. Sewed the fitted sheet (with elastic edges cut off) to a flat, quilted mattress pad; then sewed the top sheet at the bottom and halfway along one side. Made sort of a "full-sized" sleeping bag that could be thrown in the washer/dryer. Then I tossed a blanket over that, and maybe a comforter if it was going to be cold. Worked great; and wasn't hard to simply flip out over the bed. The mattress-pad bottom kept it from getting all bunched up.