Now, the the R5X GHOST - Bear Spirit is available for purchase in the Customization Menu.
This helmet could previously be won through the "RARE HELMET LOTTERY BOX", which was available post-Parity Patch, untill it was removed in the holiday update on the 18th of december, 2015.
In-game Description Edit
Light helmet. A ghostly bear adorns this version of the Allied R5X GHOST.