Think you are gonna need a custom made one. I had one made a GK trimmers in Canning Vale and have used it towing the boat up north a few times now. Even with a couple of broken straps from wearing through on the Gnaraloo track it fits snuggly and won't move as there's a bungy cord around the rim. The old story you get what you pay for, and while this wasn't cheap it was definitely a good investment.