Is there such a thing? My ds is just 5 and is now 18KG so we need to get him a new car seat. But I do think that a five point harness is so much safer that. I have seen the Britax & M & P ones but obviously at some point (soon) the harness won't fit him and it turns into an ordinary booster. Then that is not as safe as a high-backed booster used with ordinary seat belt.
Or am I just fussing un-neccessarily? Please give me an answer on this one!