The First Years On-The-Go Booster Seat – Link

Amazon has currently dropped the price on this to only $13.99, which is its lowest ever.

• Self-inflates into a sturdy and comfortable full-size booster seat
• Adjustable safety belt with T-restraint helps hold your child securely
• Self-carry handle
• Holds up to 50 pounds
• Age Grade: 9 months+