I have used several of the plastic "Goliath ganger" heads from the plastic set of Necromunda . The thick stocky neck suited its application to Empire Knights bodies quite well , they have fantastic grimacing faces ( the crooked teeth or lack thereof are very characterful ) , mind you they do have a mohican haircut , but its easily removed with a knife , i cant rmember if theu had earrings or not , but again easily removed .
I think there also might be a Catachan Jungle fighter head that is also bald , maybe ask at your local club from some of the 40K players ?
hope that helps , cheers tom