What about something larger that distributes its weight around a larger area? I have a Dakine Helipack (http://www.dakine.com/snowboard/packs/snow/heli-pack/
) with a 2 liter Platypus bladder (http://www.cascadedesigns.com/Platyp...Zip-SL/product
) in it.
The left shoulder strap has a channel to hold the bladder tube & nozzle.
You can also rig the bag to hold your snowboard (vertically) in case you have to hike a ways back to the bus/car/condo