We have a new climber on our crew with a small head, and they can't seem to get the ear muffs on our standard Vertex Petzl helmet to fit right over their ears. Their head is 20.5 inches / 52 cm in circumference. Which places them just under the normal fit for most helmets. We looked at the child helmets and lol big surprise they don't come with the kind of safety compliance features standard to the helmets we use. They tried on a Protos and that fit, but honestly a new Protos isn't something I'm super keen on pulling the trigger on at the moment. Anyone have any recommendations?