My boy has one that with cars on that he likes to wear, It also fits properly. I can't remember the brand, giro or bell I think.
We also have a rule - if he wears a helmet then so do I, and visa versa.
Nothing boils my wee more than
1) seeing parents riding sans helmet and kids with - it's either a good idea or it's not
2) Parents that absolutely insist their kids wear a helmet when they even touch a bike or scooter and then slap an ill fitting saucepan on their heads and don't even do the strap up properly.
I got evil stares from some parents a while back when my boy borrowed a go on a bike and I told him not to bother with a helmet as the only one available was too small and he'd be better off without. Their kids were happily riding around with helmets perched atop their heads feeling safe.
Sorry, I'll stop ranting now.