I had the same problem with a quilt for my granddaughter and I entertained the idea of a ruffle as it seemed quick. But then I considered that it would not be nice to fold and store. I took the binding off and put it aside to reuse. Luckily I had enough of the quilt fabric that I could add a border to the backing. Then I butted batting to what was already there, using strips of light weight fusible interfacing to hold it in place. Then I added a border to the quilt top. I was able to pin border seam on top and border seam on bottom so it looks like it was intended to be as it turned out. I put the binding back on (had to add to that, of course) and then did the quilting in the new border. I doubt anyone in the future will recognize that the quilt has been "fixed" as it looks nice, even though it was a pain to get there! Incidentally, I hand quilted this one and had no problem with the fusible interfacing when I was quilting through it.