For my 6.0, (thinner hull profile), I made my own by
finding 12"ID PVC pipe scraps at construction sites,
cut them using jig saw,
and contact cement glued carpet to them.
I would use the flatter 'stove' bolts to secure to my trailer or my cat wheels. (under the carpet, bolt, then carpet)
Worked like a charm- bascially free, or low cost (carpet scraps and gule for free also- friends)