There are some obvious items.
Uncommon items
Rare
Whether or not you want to allow non-metallic medium armor (turtle shell breastplate) is up to you.
Uncommon items
- Cloak of Protection for +1 to AC
- +1 Shield
Rare
- Armor +1
- Cloak of Displacement, effectively adds around +5 to AC.
- Ring of Protection (also rare) adds +1 to AC. Nothing stops you from having multiple rings, or stacking with the cloak.
Whether or not you want to allow non-metallic medium armor (turtle shell breastplate) is up to you.