ThinkGeek Con-Survival Bag of Holding
The Con-Survival Edition is perfect for those attending conventions, specific clear-screen opening for a tablet or map, side pockets fit in water bottles perfectly, and front hook-and-loop panel allow for patches of any size and shape. 

I brought it thinking it would be good for PAX, but with kids - I couldn't even leave home without a bigger bag! Definitely a good choice for those who just need a decent shoulder-bag to show their nerd-cred, or for taking to your next D&D game with your character sheet and dice! 
  • Hands-free hinged front pocket with clear vinyl pocket for tablet use
  • Mesh side pockets for water bottles, one with a toggle pull for holding items
  • Pass-through grommet for cable management
  • 360° swiveling carabiners to reduce tangling
External Dimensions: 14 1/2" x 13" x 4 1/2"
Interior Dimensions: 13 1/2" x 10" x 3"

From what I can see - most are selling on ebay for $100 plus $50 shipping, or about $140 in total, so happy to just go a solid $110 for the bag and inclusive domestic (Australia) postage.