If you want an instant back cover for your chair, you can use or put a t-shirt on it, on the backing, temporarily or however you want it. And
if you don't like staining your walls where you normally rest the back of your head when you're sitting you can put a shirt on a hanger and hang it on the wall with a tie or string on the said area. At both above, you can insert a cushion if you want, you can sew it or sew a tie and tie it with a tie sewn on the shirts. In the future we can use comfortable Google Shirts designed to be easily and readily converted into a comfortable chair back cover and head rests. I hope this Google article is helpful to you.......