If you sign up for an AutoDesk account, you may get decent results by using AutoDesk123D Catch to scan the person's head. After you get the file out of 123D Catch, clean it up and add a base in MeshMixer. Then bring the cleaned up file into AutoDesk 123D. AutoDesk 123D can generate common 3D interchange formats that can be converted for use with a 3D printer.  Unfortunately, I don't know of an equivalent open source workflow :-/.  Also, this is off the top of my head ;-). I have don't this workflow since last summer.