I made "shabby chic" covers for the Scamp
dinette area by just putting elastic around material cut large enough to wrap around the top and sides of the cushions. The bottom still shows the original cushion cover in the center. It seemed like it took a lot of fabric (which I found at a Goodwill Store). There were three cushions to cover: two large and one small per side. But it is really easy to pull them off and throw in the washer. They don't have a snug fit, but at least you can set on the cushions now with shorts on
You could also use a contrasting or matching fabric for the sides or bottom, if you wanted a more fitted look with a zipper closing.