Walmart offers the Cosco Juvenile Pronto Belt Positioning Booster Car Seat in Teardrop for $28.13. (Amazon charges the same for Prime members.) Opt for in-store pickup to dodge the $4.97 shipping fee. That's the lowest price we could find by $12. It converts to a backless booster and features a weight capacity of 100 lbs., adjustable headrest, and slide-out cup holder.