Gameszone.no1 via eBay offers this World Travel Vinyl Wall Decal for $2 plus 74 cents for shipping. That's tied with our September mention and the lowest total price we could find by $2, outside of the mention below. It measures 28" x 20" and is easy to apply and remove. Note that this item ships from mainland China and may take three to eight weeks to arrive.
Update: Specs corrected.