There is a currently a bug that makes it impossible to buy most of the headgears Most of the headgear(s) are now available.
Ghost Recon Online - Specialist Headgear Sept-15-12
All of the Specialist's headgear
Ghost Recon Online - Recon Headgear Sept-15-12
All of the Recon's headgear
Ghost Recon Online - Arctic Pack Armor and Headgear
The new pieces of headgear from the Arctic Pack