Unless you're really sold on the hydration bladder/hose set-up, I'd consider plastic soda or bottled water bottles. They're cheap, light (<1oz), and available everywhere. Depending on where I'm hiking, I'll carry one or two 1-liter bottles, as well as a 2-liter platy for camp. I'll carry the bottles in my pack side pockets so I can get to them, and my platy rolled up on my pack. I use a ULA gravity filter, which screws on the plastic bottles as well as the platy.