Car seat for 4 year old

[eyesbiggerthanstomach]

I have maxi cosi 2 way pearl. DS is turning 4 soon and needs to move on to the next stage. I have slight issue in that the 2 way can’t be used with a seatbelt and I am going to be car sharing as am without a car. Any recommendations. Safety is the most important thing and I would like one that fixes with a seatbelt as well as isofix. Thanks

It sounds like you want to look at high backed boosters now, they are the most practical thing when you're car sharing and although many have isofix they can also all be used without.