I am looking at sort of replicating the ULA Amigo Pro filter which, now that ULA has passed to new owners, has been discontinued. My bag sprung a leak (although I can't find a source), and due to my negligence mold developed in part of the tubing. I was hoping to buy a new Amigo Pro when ULA reopened this winter, but because of the management change it is no longer available.

The setup basically requires a 1.5 gallon (6-8 liter) silnylon bag, a Katadyn Hiker Pro filer, and a bunch of tubing. My Amigo Pro weighs about 7.5 oz, lighter than most pump filters, and filters 1 liter per second (better than I can manage with a pump and an aching lower back!).

I'll post results in the Make Your Own Gear section when (if) I get my own version together.

Like others here, I do take along some Katadyn MicroPur tablets as backup in case of filter failure, or of encountering really nasty water sources where I want to be sure I kill everything.