[Faceman]

the amulet is sold by Deirdre (same merchant who sells Plate of Balduran).
the helm of glory is a quest reward for one of the errand-quests in Atkathla
I never came across the boots, and never heard where or IF you can encounter them. They are also among the few boots that have an item code different from BOOTx. I guess that they were meant as a quest item but never made it into the game.
You should be content with finding the Helmet as it pushes you to 25 which is the max anyway.