Here's what I worked out today.
I used the Nalgene bottle method to create a bulkhead seal through a wally world nylon dry bag.
The projects you'll find online doing this also mount a filter inside the bag. I did not go that route as I intend to use a CleanStream filter hanging below the bag.
In the middle of the Nalgene bottle top I drilled a 3/4" hole with a Fostner bit because its what I had handy.
I then put a #13 oring from Lowes in the threaded side of a 3/8" barb by 1/2"MIP nylon fitting.
I found a push to connect fitting in Lowes that had a female 1/2" threaded plastic section and a brass end on the other side. Its kind of hard to describe but the female end is obviously meant to screw on while the rest remains stationary. The female part has 3 'wings' so its sort of like a wingnut. You'd know it if you saw it.
I pushed/screwed in the threads of the nylon barbed fitting onto the lid and on the inside of the lid I screwed on the wingnut to tighten things up and keep it from being able to pull out the lid. The wings work perfectly to act as a washer and make it easy to screw on.
I cut off the top section of the water bottle and left a bit of the shoulder on it. I smoothed the edges here. I've got some fine mesh I intend to stretch over the opening and secure with a rubber band to act as my pre-filter.
I then cut a hole in the center of the bottom of the bag that's probably 1-1/4" I just sort of eye balled it but it obviously needs to be smaller than the opening of the Nalgene bottle.
From inside the bag I pushed the chunk of bottle against the bottom of the bag trying to keep it centered with the hole in the bag in the middle of my bottle piece. From the outside, screwn down the lid with the fabric stuck between the two. You end up with a sack with what looks like a nalgene lid stuck to the bottom and a nylon barb fitting poking out of that.
I'm hoping to swing by REI this weekend and pick up a CleanStream filter and do some testing.
Just trying it out in the kitchen with a good gallon or so of water it was very promising. The Nalgene lid seals 100%. The fittings through the lid seal about 99%. It has a very very slow drip that wouldn't hurt anything.
I had a green thread protector from Lowes handy that fits perfectly over the barb. Its meant to push on the end of a bolt that sticks out on say a swing set and keep the metal from poking or cutting someone. It fits over the barb tight enough to act as kind of an inverted cork. This will likely be handy to stop up the barb while collecting water when I don't want hoses hanging all over the place.
I'll probably get a on/off valve and shower head fitting from REI that's meant for a camp shower bag. This will then work for water collection, especially when putting out the camp fire, as well as filtration and a shower.
I'll post pictures and weight once I've got it all put together.
It sounds like this will save me a good $30-40 over buying the whole Cleanstream and arguably do more.