5pt harness for 4yo

I need suggestions, my four year old is 46 pounds, she is not ready to be in a high back booster, I have the Natalus and HATE it, i have gotten two sets of replacement straps from graco and the bottom buckle still gets jammed all the time. Are there any other affordable options that have a 5pt harness? I was seriously considering the safety first air protect high back booster but i just cant trust her with only the seat belt. This needs to be around the same size or smaller because i have to fit it on the back seat with a my ride 65 and a safety first air protect convertable seat.

Britax Frontier 85. We love this seat...our 5.5yo [44lb 47"] is so comfy in it, easy to install, 2 cup holders, non-retreading harness. It has the highest shoulder strap slots, as well as tallest high back booster shell, so at this point the seat will last you longer than an other...which is great since it won't expire for 9years from date of manufacter!