Ebay offers Sierra Designs Bear Peak 13L Hydration Backpack for $18.99 (reg $44.99) with free shipping.

Product Description:
This deluxe hydration pack has everything you need to make it up the mountain. A 2L water reservoir is included to keep you hydrated throughout the day, and the pack’s multiple internal and external storage compartments keep all your gear organized. Not using all the storage space? Cinch the pack down using the side compression straps to provide a more stable load carry and hit the trail in comfort.

• Dimensions (Overall): 17.72 Inches (H) x 9.84 Inches (W) x 5.51 Inches (D)
• Weight: 1.04 Pounds
• Suggested Age: 12 Years and Up
• Shell Material: Polyester
• Bag Structure: Softside
• Interior Features: Hydration Bladder Sleeve
• Exterior Features: Padded Shoulder Straps, Zip Pocket, Reflective Tape, 2-Bottle Holders, Sternum Strap
• Main Compartment Closure: Zip Closure
• Handle Type: Loop Handle
• Number of Wheels: No Wheels
• Water Tank Capacity: 2 Liter
• Capacity (Volume): 13 Liter
• Garment Details: Polyurethane Coating
• Protective Qualities: Water-Resistant
• Used For: Climbing, Bicycling, Hunting, Hiking, camping
• Maximum Strap Length: 18.11 Inches
• Fits Laptop: No Laptop Pocket
• Battery: No Battery Used
• Care & Cleaning: Hand Wash