i would recommend the hydrastorm matrix..
http://www.blackhawk.com/product1.asp?P=65MT00
Designed for mountain rescue professionals, the Matrix is constructed to perform at the highest levels, while minimizing weight. Great pack for those trips when you dont want everyone to know who you are and what you do.
Drink system protected by Microban® antimicrobial technology*
Market proven bite valve and patent pending quick disconnect system
Tapered fit for extreme activities
Aerodynamic shape to minimize wind profile
Outer compression panel and threaded shock cord for rapid tool deployment
Numerous storage and attachment points
Laptop pocket in main compartment
Bottom constructed of HawkTex abrasion and moisture resistant material
Capacity: 100 oz./3 liters Cubes: 1920
Main Compartment Cubes: 1740
Dimensions: 20H X 10W X 7.5D
got mine for SGD250