On Amazon where you can now get this
Graco Tranzitions 3 in 1 Harness Booster Seat for just $97.99 shipped (regularly $139.99)!

This lightweight car seat is designed for kiddos ages 3 – 8 and transitions seamlessly from harness booster, high back booster, and backless booster. It features a Simply Safe Adjust Harness System, which adjusts your harness and headrest to eight height positions, with no rethreading.
Plus, it also has two removable cup holders, a machine washable seat pad, body insert and harness covers.