You can take the remaining cover to a fabric store and see if they have similar fabric so you could make a new one, or just get a coordinating fabric and make a matched pair. They are simple to sew, even if you don't have a machine it could be done by hand. Frankly, I think they look tacky on furniture and have only ever kept them (in a drawer) in case I needed the fabric in them to patch the upholstery.
I believe you've successfully answered your own question. Have a great life!
Or should I just get rid of the remaining cover and move one with my life...
