T.S.
Hi~
We just bought (yesterday as a matter of fact) the Safety 1st Sit, Snack & Go booster seat, and so far we love it!! It has 5 different modes, has a detachable tray, and adjusts for bigger kids. It straps to the chair (although, probably not your booth seat) and also has a strap to strap the child in. The thing that I really liked about it is that when they get older, or in the case of my chubby 18 mo old daughter, her legs don't get smooshed under the table =) It also folds up and as a carrying strap. We got it at Target for $19.99~hope this helps!!
T.