Heavy Asura Armor
You could always turn off the display of your helm. I realize that this does not directly answer your question, but if you like your hair it’s certainly an option. I myself hardly ever show helm slot items in any MMO.
To look for heavy head gear that will let your hair come through, try http://www.gw2armor.com/ or heading to the Mists (PvP icon - crossed swords - in the upper-left of the screen) and using the PvP locker to preview heavy armors.
thx I was hoping i would not have to do that but oh well :P
Personally I don’t know why you would want to show the hair, but each to their own.
Check this website out http://argos-soft.net/GW2ArmorGallery/index.php?weight=3&race=0&color=10&sex=0 it shows all the armour types on a model character. Just quickly scanning through I think maybe Tier 1 or Tier 2 cultural armour will show the hair (haven’t tested in game).