Fortunately, I took the coat with me to the fabric store because my first ideas - red, purple, or print - were not right for it. I laid colours beside it until it was very clear that I got it right.
I had a little repair work to do. Adding a hook and eye where one was missing was easy. I also had a mishap involving iron-on pellon that I do not like to describe.
Here it is finished:
I added this scarf-like thing because there were short exposed seams on each side that indicated that something had been attached there. This may or may not be the answer.