I saw something great at the sports authority. It was a waist bag with the bag in the middle portion and on each side was a water bottle . I am going to buy 2 of them. I will replace the water bottle that they give you with the brita ones. I do not know if they have them online but at the store they were selling them for $19.99 each. A little high but I am looking for a bag and the cheapest I have found was $10. Then $3 each for the straps which will equal to $16. So for $4 more its all in one. Check it out. It seems less bulky.
You can find the Brita Water Bottles at most department stores like Target, Wal-Mart, and K-mart. I even saw them in my local grocery store.
They run about $6 a piece. We used ours when we went to WDW in August and it really made a difference in the taste of the YUCKY Orlando water.
Hope that this helps!
We got this cool Safari Mickey water bottle holder in the AK. It's sort of like a "sheath" for the bottle, with an adjustable strap. Very comfy and easy to tote around the parks. It cost around $6.