It looks like that item just covers the rear panniers on a bike, not the entire bicycle.

You could always take a cheap blue tarp, cut it to size, and sew up the sides to make a large envelope to slip over the rack and bike.

Mine just goes naked when it is on a car rack, but I don't leave it there for long periods. I would want to have a really good lock attached if that was where I habitually stored my ride.