IMHO, armor/shields with +1/+2/+3 are always good choices. You can't go wrong with a higher AC. Other special types of armor (invulnerability, of resistance) and shields (arrow-catching, animated) also make you a better tank.
Items that improve your Ability Scores (Amulet of Health and Gauntlets of Ogre Strength are some examples) are good choices too, though I can't recall any that improves your CHA score besides the Ioun Stone.
But I'd strongly recommend both the Ioun Stone of Reserve (which will store a spell of up to 3rd level until you cast it) and the Pearl of Power (retrieves a spell slot up to 3rd level once, rechargeable on the next dawn), giving you two extra casts of Fear.
Remember that most of the best items require attunement, limiting you to up to three of them.
Hope I have helped in some way!