Companion armor

Act 1

 * Heirloom Amell Protective Sigils (Bethany)/Fereldan Girded Plating (Carver) -- found in final room during the Birthright quest.

Act 2

 * Lyrium Weave -- Mage Goods shop (Gallows)
 * Armor Struts -- Lirene's Fereldan Imports shop (Lowtown)
 * Spirit Essence -- found in the Gallows Dungeon during the Dissent quest

Act 3

 * Sigil of the Mage Underground -- found during the Best Served Cold quest

Act 1

 * Underpadding Guardsman Pattern -- Armor Merchant shop (Lowtown)

Act 2

 * Flex-Chain Guardsman Pattern -- found on Fell Orden during Raiders on the Cliffs quest
 * Impact Plating Guardsman Pattern -- Armor Merchant shop (Lowtown)

Act 3

 * Deflecting Joints Guardsman Pattern -- found on Jeven during Favor and Fault quest

Act 2

 * Lyrium Scales -- Shady Merchandise shop (Docks)
 * Tevinter Spirit Symbol -- Robes by Jean Luc shop (Hightown)
 * Reinforced Straps -- found in Abandoned Slaver Den during A Bitter Pill quest

Act 3

 * Enchanted Resin -- found on Dragon during Mine Massacre quest

Act 2

 * Lambswool Insoles -- found in Lost-End Foundry during To Catch A Thief quest
 * Rigid Boning -- Apparel Shop (Lowtown)
 * Supportive Corselet -- Robes by Jean Luc shop (Hightown)

Act 3

 * Boiled Leather Plates -- found during A Murder of Crows quest

Act 2

 * Silver-Threaded Dalish Embroidery -- Sundermount, near the top of the path
 * Carved Ironwood Buttons -- Ilen's Crafts shop (Sundermount)
 * Samite Lining -- Robes by Jean Luc shop (Hightown)

Act 3

 * Halla Horn Buckles -- found on Pride Demon during A New Path quest

Other

 * Raiments of the Dalish Pariah -- if romanced

Act 1

 * Inscribed Leather Harness -- Apparel shop (Lowtown)

Act 2

 * Silverite-Reinforced Buckles -- found in Bartrand's Estate during Family Matter quest
 * Coat Lining with Concealed Pockets -- Shady Merchandise shop (Docks)

Act 3

 * Drakeskin Leg Straps -- [spoiler]

Act 2

 * Enhanced Articulation -- Armor Shop (Gallows)
 * Mail Undertunic -- found in Harriman Estate during Repentance quest
 * Reinforced Bracers -- Olaf's Armory shop (Hightown)

Act 3

 * Protection of the Faith -- found on Templar Lieutenant during Best Served Cold quest