Bobblehead - Barter is a Fallout 3 Vault Boy Bobblehead item. It permanently improves your character's Barter skill by 10, to a maximum of 100.
It is found at Evergreen Mills Bazaar', in a dark cave-nook, in the corner of the room to the right of Smiling Jack. Jump over the work bench, it's on the right-most shelves.
Obtaining Bobblehead Barter