You asked about filters... are you open to other types of treatment?

I use a steripen and am very happy with it. The thing is super lightweight and treats water in about 1.5 minutes. The first ones they came out with didn't work very well but recent models seem pretty reliable. Let me know if you have any questions about it.

In terms of filters a lot of people seem to like the sawyer gravity (or squeeze) systems. I've never used one, but it is the most common one I hear about.

I have used an MSR miniworks multiple times and its a nice filter and works well. It is good for reaching down to hard to access water.