Does he have masterwork armor? Feyleather armors start at level 16 (minimum enhancement +4), which is easily available in treasure parcels for level 14. Alternatively, hide armor proficiency can help, the corresponding masterwork armor is Darkhide (also starting at level 16).
Both Davros Elden's Defensive Step (Lvl 7 Grandmaster Training, DMG2) and Boots of the Fencing Master (Lvl 7 Feet Slot, AV) give +1 AC and Ref when you shift.
Steadfast Boots (Lvl 8 Feet Slot, AV) give +2 to all defenses for as long as you stay in one place.
Dragonborn Greaves (Lvl 12 Feet Slot, AV) give +1 AC and Ref while you're bloodied.
The Cloak of Displacement (Lvl 10+ Neck Slot, AV, MME) gives +2 AC and Ref until you're hit for the first time in an encounter.
The Amulet of Elusive Prey (Lvl 14+ Neck Slot, AV) gives +2 AC and Ref for as long as you've moved at least 4 squares on your turn.
The Elven Chain Shirt (Lvl 9+ Wondrous Item, MME) stacks with light armor and gives +1 AC (+2 @ Lvl 19).
There is an amor in AV1 Agile Armor which does give him a bonus AC depending on his DEX mod. It limits it of course, but he is 1 level away from being able to get +2 AC.
Agile Armor is for chain, scale, or plate armors only, so that won't work for most rangers.