Technique: Glyph of Mana Shield

The Technique: Glyph of Mana Shield was sold for by the following NPCs:
 * at Honor Hold (Hellfire Peninsula)
 * at Thrallmar (Hellfire Peninsula)
 * in the Scribe's Sacellum (Dalaran)

It is limited supply, but has a fast respawn timer (approximately 1-2 minutes).