There are two other +3 shields I am aware of. In act two, behind the bugbear trader. There is a merchant in early act three that sells one. Both have no special abilities
Some other magic items I found: Gonna keep updating as I go, -The pointy hat is in the chest behind Lucretia -you can pickpocket the absolute confidence amulet from Naaber in carms and garms and after exhausting his dialogue options after stealing the necklace he rewards you with the seemingly gleaming ring -the scarlet leather armor is in the hidden room behind the wardrobe on the third floor of the flophouse next to sharess caress
I forgot to mention this, after find Tara at the devil's fee, you can find her at the roof of the wine festival building for the last time and get the slinging shoe
Also, if you were not able to get the Ring of Mind Shielding from the Mind Flayer from the Underdark, you can get it when you go to the Iron Throne to save the Gondians and Duke Ravengard, it’s in the backpack next to the table that the Mind Flayer is laid out on.
"If he sees Shadowheart" is the keyphrase hear. All confusion aside, if he never sees Shadowheart, he will never run off regardless of any prior choices.