I made my own from some vinyl sheet. it's about 4mm thick,really flexible,but rigid enough not to fold back during driving.
I made the brackets from the perforated metal strips used to hold roof timbers together,not the thin ones,the thick strong ones.
They were very low to the ground before I lifted the truck,but kept the back of the truck clean. Off road I tie them back if there is going to be a chance of reversing over them