Shop Cosco Topside Booster Car Seat online at Macys.com. Give your child a comfy lift with the Cosco Topside Booster featuring an extra-plush pad. This booster gives them the extra height they need to keep seatbelts properly positioned. Super lightweight, it's simple to move from car to car and features a seat-safe design that leaves your car seats smooth and unmarked when switching vehicles. Comfy and lightweight, the Topside Booster is great for families on the go.