Luggage roof rack cover

[Campingbuddy]

Does anyone know if there is such a thing as a waterproof vinyl luggage protector? I have seen some on luggage racks on some vehicles. I will have luggage in the back of my truck and was planning on using trash bags to cover in case of rain. However someone mentioned to my son about the protector used on roof racks. Our last trip to Disney we spent 7 1/2 hours driving in rain.

Does anyone know where I can purchased one of these covers?
Thanks