Bulky Armor is a mission-specific item for the sidequest Ell In Shining Armor.
The Bulky Armor is found by the Southeastern corner of Old Glenn the Blacksmith's Cottage
Sturdy and protective (like armor, you know, should be}.
Give it to Ellie at the end of Ell In Shining Armor to receive a Blue Shield for your efforts.
Ellie will now look like this in town: