What would be the best yo-yo for a 6 year old boy to start with?

My grandson just met his first yo-yo. He is interested, but frustrated. Of course he isn't interested in tricks of any kind yet, he just wants it to go down and come back up to his hand without stopping or getting twisted up. He's even having a hard time trying to wind it. What kind of yo-yo would be good for a VERY young, extreme beginner, and where would I find it?