Going To Need A Bigger Bag

Patch 5.4.8.: This achievement is now Account-wide.

LIST OF LOCATIONS in alphabetical order:

Old MoP items - most of them are retroactive.

• 
  
• [item=86565] - Drop from [npc=51059] or 5.4's [npc=72875]s
• 
  
• [item=106130] - Drop from [npc=72877]s or [npc=72895]s. However, with the latest hotfix, the old version of the bag dropped by [npc=50333] and 5.4's [npc=73171] is renamed to "Huge" and therefore does not count towards the criteria anymore.
• 
  
• [item=86569] - Drop from [npc=50339] or 5.4's [object=222686]s inside the Cavern of Lost Spirits
• 
  
• [item=86574] - Drop from [npc=50356] or 5.4's [npc=73174] (both original and summoned versions)
• 
  
• [item=86566] - Drop from [npc=50332] or 5.4's [npc=72895]s
• 
  
• [item=86584] - Drop from [npc=50789] or 5.4's [npc=73161] and [npc=72045]
• 
  
• [item=86580] - Drop from [npc=50766] or 5.4's [npc=72777]s
• 
  

Timeless Isle items:

• 
  
• [item=104329] - Drop from [npc=72898]
• 
  
• [item=104305] - Drop from [npc=73170]
• 
  
• [item=104302] - Drop from [npc=73171]
• 
  
• [item=104297] - Drop from [npc=72894]s and [npc=72896]s
• 
  
• [item=104304] - Drop from [npc=72897]s
• 
  
• [item=104336] - Drop from [npc=73021]s
• 
  
• [item=104321] - Drop from [npc=72048]
• 
  
• [item=104328] - Drop from [npc=72888]s
• 
  
• [item=104288] - Drop from [npc=72767]s
• 
  
• [item=104038] - Loot from the weekly [object=220832] in the the shipwreck south of Old Pi'jiu. The key for the chest is a rare drop from [npc=71920] mobs nearby.
• 
  
• [item=104320] - Drop from [npc=71864]
• 
  
• [item=104309] - Drop from [npc=72896]s
• 
  
• [item=104289] - Drop from [npc=72877]s and [npc=73277]
• 
  
• [item=104299] - Drop from [npc=73175]
• 
  
• [item=104035] - Drop from [npc=72193]
• 
  
• [item=104263] - Drop from [npc=72809]s and [npc=72970]
• 
  
• [item=104261] - Drop from [npc=73162]s and [npc=73175]
• 
  
• [item=104258] - Drop from [npc=72769]
• 
  
• [item=104313] - Drop from [npc=73157]
• 
  
• [item=104334] - Drop from [npc=73025]s
• 
  
• [item=104262] - Drop from [npc=72970] or [npc=72809]s
• 
  
• [item=104296] - Drop from [npc=72894]s and [npc=73170] at Firewalker Ruins, [npc=72897]s and [npc=73173] at Ordon Sactuary
• 
  
• [item=104298] - Drop from [npc=73172]
• 
  
• [item=104292] - Drop from [npc=72841]s or [npc=73163]
• 
  
• [item=104268] - Drop from [npc=72805]s, [npc=72808] or [npc=72049]
• 
  
• [item=104286] - Drop from [npc=73167] or [npc=72876]s
• 
  
• [item=104303] - Drop from [npc=72245]
• 
  
• [item=104269] - Drop from [npc=73167]
• 
  
• [item=104294] - Drop from [npc=73281]
• 
  
• [item=104293] - Drop from [npc=73166] and all those elite crabs around the isle.
• 
  
• [item=104290] - Drop from [npc=72908]s and [npc=72909]
• 
  
• [item=104312] - Drop from [npc=72771]s or [npc=73157]
• 
  
• [item=104306] - Drop from [npc=73173]
• 
  
• [item=104335] - Drop from [npc=73018]s
• 
  
• [item=104331] - Drop from [npc=73169]
• 
  
• [item=104330] - Drop from [npc=72892]s
• 
  
• [item=104287] - Drop from [npc=72762]s and [npc=73158]
• 
  

New battle pets:

• 
  
• [item=104156] - Drop from [npc=73277]
• 
  
• [item=104157] - Loot from [object=222685]s
• 
  
• [item=104202] - Loot from [npc=72007]'s chests
• 
  
• [item=104160] - Drop from [npc=71826]s that spawn exclusively in the Neverending Spritewood event. You can find more info here.
• 
  
• [item=104161] - Drop from [npc=73163]
• 
  
• [item=104169] - Drop from [npc=72775]
• 
  
• [item=104307] - Drop from [npc=72769]
• 
  
• [item=104164] - Drop from [npc=72767]
• 
  
• [item=104166] - Drop from [npc=73162]
• 
  
• [item=104159] - Drop from [npc=73282]
• 
  
• [item=104167] - Drop from [npc=71919]
• 
  
• [item=104168] - Drop from [npc=73166]
• 
  
• [item=104291] - Drop from [npc=72909]
• 
  

"We don't want you holding onto every item in the game" ~Blizz

So we are going to add ton more items.

My plan is to get this achievement on my 87th birthday, shortly before dying of cancer.