It’s called the Bag of Holding, and it’s logo has a 20-sided die. That’s a D&D reference, a Bag of Holding being a magical bag that can hold more inside than physically possible, via magic. For example, you could hide an entire suit of +3 Chain Mail in a purse-sized bag, and not suffer any penalties to your Encumbrance score.
Now, we could be like every other blog and make a joke about how this bag “would be suitable for any adventure, from slaying dragons to downing mead at the local Public House” or “you’ll get a +2 bonus to your style roll” or something else, but we’ll spare you all that pain.
It’s adjustable, has many pockets for your gear (because you do have gear), and actually looks quite nice for $27.99 (if you’re a geek). It’s available at Think Geek.
Bag of Holding [Think Geek]