From Reader Tip:

Got a tip that Aquapac, UK-based top quality waterproof protective case company, is offering a clearance sale on Waterproof Backpack. Now... this offer is for the US customers.

The backpack is 100% PVC free, has large pockets inside, removable support etc. etc... to list a few.

Better yet... it's half off! The downside is you cannot get this at this price if the stock is gone.

Check out their website: http://www.aquapac.net/usstore/wet-dry-25l-br-waterproof-backpack-br-code-780-2088-0.html