ThinkGeek has a bunch of their backpacks and messenger bags on sale for $10 + $6 shipping = $16 shipped. Includes this Game of Thrones Westeros Map Adventurer's Messenger Bag for $16 shipped (MSRP $60).

• Rolltop Backpack of Holding for $16 shipped
  
• Olde Book Backpack for $16 shipped
  
• Messenger Bag of Holding for $16 shipped
  
• Breath of the Wild Shield Backpack for $16 shipped
  
• Jon Snow's Backpack for $16 shipped
  
• Warcraft Alliance Shield Backpack for $16 shipped
  
• The Cache Backpack by Pixelle for $16 shipped
  
• Game of Thrones King's Landing Messenger Bag for $16 shipped