water bottle input needed

Nalgene has the 1L collapsable bottle. It has a wide mouth and weighs less than the hard bottle.

Gatorade?

Target has Embark brand water bottles, 1 liter BPA free Tritan copolyester, wide mouth like a Nalgene, but non-compatible threads [darn!] 4.9oz, $1.24 each.

Ditto on the wide mouth soft Nalgenes. Great if your pack pockets meld with them.

Nalgene makes a white polyethylene bottle that is the same dimensions as the clear ones so you an use someof the acessories too. 3.5oz and $8.50 at REI. It is my choice for use with the Steripen. I added a compass top to one as my backup. http://www.rei.com/product/402049

Check out this thread and my response:
Gatorade Bottle SteriPen Adapter

I agree with Travis.
I bought 2 of these myself and I weighed them at 2.4oz! You can't go wrong with that weight.
Here is a pic:

Here's a link to BPLs store for them:

http://www.backpackinglight.com/cgi-bin/backpackinglight/nalgene_cantene_water_bottle_1L.html

Interesting that the material makes a big difference in the weight — you decide if any of these weights are acceptable for your pack.

Nalgene semi-rigid container, High-density Polyethylene, 3.5 oz

Nalgene hard container, Tritan copolyester, 6.2 oz

Nalgene collapsable, Polyethylene, 2.0 oz

Compare that with the Platypus collapsable container at .8 oz.!!

Personally I find the Platy works great for all conditions.

The Journey comes with the tapered tip that fits platy bottles and similarly sized soda/water bottle openings. It might make more sense than using heavier wide mouthed bottles, if you aren't able to use a cooking container to treat the water.

For example, the platypus weighs 0.8oz, while the 1L nalgene collapsable canteen weighs in at 2.1. That is a difference of 1.3oz.

The Sterpien Adventurer weighs 3.6oz, while the Journey 4.5 oz, a difference of 0.9oz.

By choosing the heavier Journey, and the lighter bottle, you save 0.4oz.