Car Seats

I am a  great grandmother of a almost 3 year old. I am on my 3 lot of car seats am trying to find one that is Harley proof. He manages to undo the straps whilst in the car. I jut saw the advert for a car seat hence the thread. Can anyone tell me a little bit more about this car seat i.e cost and how toddler proof is it. Many thanks. Grandmaj