Sentinel's armour is a tricky one to find. The shoulders are mail, and so I have found some other mail gear that gives the same colour and a simular look to the Sentinels that we find in game.
Impenetrable Pauldrons
Abyssal Mail Greaves
Scaled Greaves of Patience
Impenetrable Breastplate
Fathomheart Gauntlets
Frostreaver Crown
Netherfury Belt
