I really like my Steripen for water purification, and Aquafina bottles are nice and light, but the Steripen obviously does not fit inside. What to do? Carry a Nalgene? Too heavy! Cut up a Platypus or Nalgene canteen? Light but awkward.
It occurred to me that a 1 liter Aquafina bottle would probably fit into a 1.5 liter Aquafina bottle with the top cut off. The open 1.5 liter bottle would be very light, and yet wide open to the Steripen.
I emptied a 1.5 liter bottle, then filled it with 1 liter of water, marked that, and found it came to a bit more than half an inch from the upper edge of the label section, about the bottom of the setting sun. I cut the top off right where it flares out.
The photos below (sort of) show the results. Sorry, but the camera really did not want to focus on the transparent plastic. But I think there's enough to show the idea when combined with the verbiage above.
The first photo shows a 1.5 liter bottle, full, a 1.5 cut just above the 1 liter mark, and a new 1 liter bottle.
Photo 2 shows the new 1.5 liter bottle, and the cut 1.5 with a 1 liter inserted. The fit is not snug (the inner bottle will fall out if you turn the outside bottle upside down), but holds it pretty well; if you have any sort of bungie top to your side pocket, it will compress the outer bottle and hold things well. The bumps on the inner bottle bottom fit well into the bumps on the outer bottle bottom.
I think I've found the solution to my Steripen and Aquafina bottle dilemma!