Here is a list of some of the seats you may want to look at. The taller the belt guide, the longer it will last height wise. Please note that some may fit a child better then others so it is often best to try them out and see which one works best for your child and your car.
Graco Turbo Booster - belt guide fits 19" torso, up to 100lbs
Graco Air Booster - belt guide fits 19" torso, up to 100lbs. This booster is deep so it works well with kids with longer legs.
Compass B5510 - belt guide fits 19" torso, up to 100lbs. Seat folds up so it can be stored easily.
Britax Monarch - belt guide fits 20" torso, up to 100lbs
Britax Parkway - belt guide fits 21" torso, up to 100lbs. Very narrow so it works well in tight spaces. This seat is being discontinued so it isn't always easy to find.
Ricaro Vivo - belt guide fits 21" torso, up to 100lbs
Jane Indy - belt guide fits 21" torso, up to 80lbs. Can use latch to secure in the car
Recaro Start - belt guide fits 21" torso, up to 80lbs. Very adjustable to fit child's size. Can use latch to secure in the car, though I think it does require a top tether.
Sunshine Kids Monterey - belt guide fits 22" torso (though some seats seem to only go up to 20-21"), up to 120lbs. Can use latch to secure in the car.