I make mine out of fillets
No, wait .... you're talking about cover "never mind"
But seriously ... there's a whole forum on this !! And from what I've read : PVC, cedar trees, bamboo, palettes, wooden stakes, piles of tree limbs, and a whole bunch of other stuff has been used. I don't know as there's a "better option" ... so long as you put that cover in the appropriate place, and it's legal to do so. That & understand that once it's in the water ... it's "public property" (& with today's electronics, likely to be found & fished fairly quickly).
... cp