My almost 5 year old is using the Britax Pinnacle High back booster. I wanted to get a cheaper "extra" car seat for grandparents car that's similar.

It needs to be:
Booster seat
High back
Harness straps
not as expensive as the Britax

any recs??

PSA: Target is doing a trade in event. (https://corporate.target.com/article/2017/04/terracycle-car-seat-trade-in?clkid=42577a29N2b69848310e699225bfd670d&lnm=81938&afid=ShopStyle+Inc.&ref=tgt_adv_xasd0002)
We were gonna trade in her infant car seat (expiring next year) for the extra carseat.