This is a list of all the remaining vendor, profession, instance and raid sources I have yet to collect. A blog post will be added to reflect any changes.

Vendor

Grand Expedition Yak

Jewelcrafting

Jeweled Onyx Panther

Engineering

Sky Golem

Level 70

Time Lost Proto-Drake – Rare

Raids
Fiery Warhorse’s Reins – Karazhan – Attumen the Huntsman
Ashes of Al’ar – The Eye (Tempest Keep) – Kael’thas Sunstrider

Level 80

Instances
Reins of the Blue Proto-Drake – Utgarde Pinnacle (Heroic) – Skadi the Ruthless

Raids
Reins of the Grand Black War Mammoth – Vault of Archavon – All 4 Bosses
Reins of the Azure Drake – The Eye of Eternity – Malygos
Reins of the Onyxian Drake – Onyxia’s Lair – Onyxia
Mimiron’s HeadUlduar – Yogg-Saron (No Watchers – 25)
Invincible’s Reins – Icecrown Citadel – The Lich King (Heroic – 25)

Level 85

Reins of the Phosphorescent Stone Drake – Aeonaxx

Instances
Reins of the Drake of the North Wind – The Vortex Pinnacle – Altairus
Reins of the Vitreous Stone Drake – The Stonecore – Slabhide
Swift Zulian Panther – Zul’Gurub – High Priestess Kilnara
Armored Razzashi Raptor - Zul’Gurub – Bloodlord Mandokir

Raids
Reins of the Drake of the South Wind – Throne of the Four Winds – Al’Akir
Flametalon of Alysrazor – Firelands – Alysrazor
Smoldering Egg of Millagazor – Firelands – Ragnaros
Experiment 12-B – Dragon Soul – Ultraxion
Reins of the Blazing Drake – Dragon Soul – Deathwing
Life-Binder’s Handmaiden – Dragon Soul – Deathwing (Heroic – 10/25)

Level 90

Ancestral Phoenix Egg – Challenge Conqueror: Silver
Amber Primordial Direhorn – Zandalari Warbringer
Bone-White Primal Raptor – 9999 bones

World Boss
Reins of the Heavenly Onyx Cloud Serpent – Kun-Lai Summit – Sha of Anger
Son of Galleon’s Saddle – Valley of the Four Winds – Galleon
Reins of the Thundering Cobalt Cloud Serpent – Isle of Thunder – Nalak
Reins of the Cobalt Primordial Direhorn – Isle of Giants – Oondasta

Raids
Reins of the Astral Cloud Serpent – Mogu’shan Vaults – Elegon
Spawn of HorridonThrone of Thunder – Horridon
Clutch of Ji-KunThrone of Thunder – Ji-Kun

Thanks to Sickbox on WoWHead for compiling most of this info. I know there are more but these are the most obvious.