LightInTheBox offers the Bluefield 70-Liter Waterproof Floating Dry Bag in several colors (Green pictured) for $8.99 plus $1.67 for shipping. That's the lowest price we could find by $5, although we saw it for $3 less in March. It's fully waterproof and the clip doubles as a handle.

Note: This item ships from China and may take two to three weeks to arrive. Uncheck "Add Shipping Insurance to your order" during checkout to remove the 49-cent fee.