A.M.
I have a 2 1/2 yr old in a convertable car seat & recently had to get a new seat for my now 13 month old. Money was tight, but I wanted them to be safe. Under 4 is legally too young for a booster & unsafe (I was gonna go that route too until I researched this). I am all about Craigslist, but the one thing to not get second hand is a carseat, especially one that has been in an accident. I ended up (& recommend) going to Big Lots. I got a Safety 1st forward facing seat (Summit Deluxe) that will also convert to a booster for $40. It's normally $60, but Big Lots has it on sale a couple times a month. My son & I love it. It's 2/3's a convertable car seat (just w/o the rear facing part). Good luck & let us know what happens!