I imagine they'd be easy to fix if you can sew even a little bit

Find the part where it's been top stitched. From memory it's where the snaps are at the front. Unpick that bit, turn it inside out and sew elastic over the old stuff. Then flip back right side out and sew it closed again. Just be careful not to create any pin holes in areas other than the seam allowance if you use them.

Another way you could do it is to feel your way along where the elastic is and cut a little slit either end, thread the elastic through, sew one end down and pull it tight and sew the other end. I don't think you'll get as nice a result that way though.