Grizzly Bear Skins
 

May want to check if they are dropping still. Must have killed over a hundred grizzlies and only skin drops are: ruined, low, medium, high and thick. The regular grizzly bear skin is needed for the Leatherfoot Raider Skullcap quest.

Edit: did finally get a Grizzly Bear Skin, however, the drop rate seems way to low.

One in over a hundred has been my experience as well, but i don't really think its a bug - just part of what makes the cap collection quest so painful. :)