The game's collection data lists Synapse-String Handguards as sold by 2 vendor NPCs in The Summer Terrace and Stormshield.
Vendor
Zone
Map
Waypoint
Other items it sells
NPC #77440
The Summer Terrace
-
-
2
NPC #93907
Stormshield
-
-
171
Vendor NPC, zone and position come from the client's collection source tables (CollectableSourceInfo and CollectableSourceVendorSparse); coordinates are the in-game map readout.
Build history
First seen in build 5.5.4.69585 (Mists of Pandaria).
Read from the World of Warcraft client build files.
How Synapse-String Handguards Compares
Who It Suits
Mail is the armor type Evoker, Hunter and Shaman wear. With Agility or Intellect, Synapse-String Handguards suits Beast Mastery, Marksmanship and Survival Hunter; Elemental, Enhancement and Restoration Shaman; Devastation, Preservation and Augmentation Evoker.
4 other items in the current build are also called Synapse-String Handguards. Same-name entries are usually a different rank, faction, quest stage or reward track of the same object.
Blizzard numbers items as they are created, so the named items next to ID 96123 (96118 to 96128) were usually added in the same batch as Synapse-String Handguards: the same quest line, zone, vendor or reward set.