At the end of small path jutting off of the long looping path to the west, destroy the Morgul object on the treasure chest to grab another Mithril brick. At night, burn down some wood on the long looping path to the west to nab a Mithril brick. The Mithril brick will appear near some reveling Hobbits. Travel to the middle of Hobbiton during the night (use the Map Stone to switch times) and use Sam to fire off some fireworks. East of Bag End, around the path where you buy Tom Bombadil, whack 10 moles in 25 seconds to earn a Mithril brick. On the far west end of Hobbiton, use Legolas to shoot the targets that pop up in the field for another Mithril brick. West of Bag End, use Gimli to break the Cracked Lego tile for the Mithril brick.
On top of the hill outside of Bag End, use Sam's spade to dig up the Mithril brick.
