Check out
www.veada.com. I did not purchase there, but I was considering doing so before opting to just go with a 128 quart cooler with cushion. Their seats are custom made with up to 3 different color panels and any height base from 8 to 18". However, I thought your V21 had the fish box base. Are you going to get rid of the fish box? If not, they do sell just a topper (no base) which may work with your fish box. Free shipping too on any order over $250.