You have to know where to look. You can often buy odd sized and left over scrap pieces at a commercial truck & trailer supply place. They use the black stuff to line the bottom of dump trailers so product slides out easier.
Yamaha sells a sweet glide plate for the Grizzly, maybe on for the Wolverine will be out soon? The only issue for me is that the plate holds a lot of mud and crud on the topside and is a little chore getting it all out with a pressure washer. Probably even worse with a large Wolverine glide plate.