Staples is offering a Thule backpack for only $32.99 (the same backpack sells on Amazon for $79.95. Info on how to save an additional $5 can be found in this SlickDeals thread.
Also note that the Alaska MileagePlan Shopping Portal 8X offer is still alive at the moment:
How can Staples sell this backpack so cheaply? Apparently they make up for their losses by selling this one too . Think of how many miles you would earn though!