Are little girl is 36 lbs., and a bit on the chunky leg side we can not find any carseat to meet this need alo?

all the harness ones on the biggest level are too tight on her legs, and pinch her. she is big enough to move up to a high back with the seat belt system, however i need a wider one, one that when she falls asleep her head doesnt fall forward. adn of course overall is very safe. any suggestions on which one and where to find it would be awesome! thanks!