Had a neighbor fix the back of his bimini top on his boat about 10years ago which had a couple of the push snaps pull away from the bottom of his canvas (Same issue you have - but it happened because he was never gentle when removing the rear panel). A Boat canvas shop pulled the 12 bottom snaps off, then ended out sewing on 1.5" round canvas patches over each of the holes (he only had two pull out, but to make it look uniform they did them all), and put new snaps on. The color wasn't an exact match, but still looked good because they were all done the same way. It was also considerably less expensive than replacing the canvas panel.
I would think the same concept would work for you.