We got all new cushions from Scamp
[our originals were vinyl on one side, too], but we also wanted to protect the new cushions from our dogs. We're very happy with the denim covers I made.
My sewing ability is limited so I made them like big pillow cases. I think the material was 60" wide. Rather than cutting off the extra width for a closer fit, I kept the extra width and tuck it in at the ends of each cushion, and the covers hold in place very well. Pre-shrinking the fabric is important. I also made the covers a few inches bigger than the actual cushions so they go on and off easily.
Good luck with your project.