I've used Spidy Gear - Bed Web nets for pickups and Spidy Gear Luggage Web nets for SUVs. They are very well made and very adjustable. The Luggage Web, which is smaller and comes in two sizes, is better suited for a Sentra. I have the larger one in the back of my FJ. It can cover a large cooler, milk crate, and ammo box with room left to expand.
I never bought a OEM net as the prices were high.