Head enchants are done by:
a) Librams (BoE) - drop randomly in higher level pre-BC dungeons/outdoor areas. They get converted to an appliable soulbound enchant 'item' by NPCs in Dire Maul library or Burning Steppes, but require several other mats and about 30 gold for each conversion. Different librams apply different enchants.
You can get a higher level to collect the mats needed and apply the enchant to a head/leg item (applied like a normal enchant, trade window open, your armor goes in the 'not to be traded' window). You CANNOT farm this on a higher toon and mail it to a twink.
b) Glyphs (BoP) - these are gained from quartermasters in Outlands, usually at revered rep, and only work on items above 60 (I believe) - applying the enchant makes the now-enchanted item soulbound, so non-transferable.
Edited, Oct 9th 2007 6:09am by Tanq