Okay, so I still carry a heavy ol' Katadyn Hiker water filter, haven't changed over to an Amigo-type system. If I can avoid plastics I generally do (and yes, that's an odd thing for an outdoor industry person to say, but I do still use and believe in many of our synthetics, but that's a discussion for the philosophy forum). I've started using the Klean Kanteens, but wanted the convenience of a MSR Miniworks screw-on type connection.
Basically, I just cut the bottom off a Klean Kanteen stainless cap, added a valve (so I could use just the one cap, not carry a separate adaptor), and some aluminum tubing. While I was at it, I've been frustrated by having my plastic tubing washed into the shallows by weak winds and wave action, so I added an aluminum "dirty" line. It seems to be great for sticking out a couple feet from shore in cleaner water and staying there. Weight-wise, ended up with a weight penalty of about 1.5 ounces. Would be nice to find a much lighter valve. But this was basically just a concept experiment.