Century Martial Arts has a few selections. Keep in mind a "cage" will obstruct his vision more so than normal head gear. You may want to consider one with a plastic visor instead. Just a thought
Macho makes good stuff:
http://www.centuryfitness.com/webapp...19&crumb=13501
Here's a Century one with less vision obstruction:
http://www.centuryfitness.com/webapp...19&crumb=13501