I am feeling really desperate in my search to find my very tall daughter a great car seat in the US. My daughter will be six next week, but is already 50 1/2” tall and about 50 lbs. We feel like she is ready for a high-back booster, but she seems to be too tall or close to too tall for most of them. Ideally this car seat would convert to a backless booster, but that isn’t a must. I’ve spent hours online and feel like I have no more if a lead. TIA!