Amazon has this Graco Tranzitions 3 in 1 Harness Booster Seat, Proof for $74.99 was $99.99!
Three seats in one: 5 point harnessed car seat, high back belt positioning booster seat and backless belt positioning booster car seat
Converts from 5 point harnessed car seat (22 to 65 pounds) to highback belt positioning booster (30 to 100 pounds) to backless belt positioning booster (40 to 100 pounds)
Simply Safe Adjust Harness System adjusts the height of your harness and headrest, in one motion, to ensure that your child is always properly secured. Harness straps may be spot cleaned
The AAP and NHTSA recommend that children should use the built in harness system until they reach the maximum forward facing weight or height for their car seat, and after reaching the maximum forward facing weight or height
Side Impact Tested; New Car Assessment Program (NCAP) peak crash force approximately 2X car seat standard; Extreme Car Interior Temperatures. Buckle may be cleaned with a damp cloth