My ds has figured out how to undo his harness buckle on his car seat so now climbs out. He's a little young to understand how dangerous it is and just likes escaping (he's always been a houdini). Its also a little difficult to reason with him about not going anywhere until he's strapped in properly. I've seen the buckle clasps for ordinary seat belts but have never seen one for a car seat buckle (we've got a Klippan). Any ideas how to stop him escaping without it meaning I've got to sit in the back with him?