Like the "Dude" I use the Katadyn Hiker Pro. Maybe a bit bulky for some but I have used water from sources that your steripen isn't going close to. Once I have run through my carry on supply of water, 100+ oz, I pump and boil all my water. A friend had a steripen on a Colorado trip and wouldn't you know, somebody forgot batteries. Lucky for him and others somebody had a Katadyn. I'm sure there are many options, this is mine and it's never failed.
"You have the rest of your life to solve your problems. How long you live depends on how well you do it."