Seems like you are looking for All-in-1 child car seats.
Need more info so can give u relevant advice:
1) What car are u driving?
2) U planning to use seat belts or isofix/latch?
3) Are u planning to have more than 1 child car seat at the car rear seats?
4) What are you priorities in sequence?
(Eg. All-in-1 type, budget, safe, convenience, light weight, narrow width, etc)

PS: I dont sell child car seats so dont worry..