Re: ideas on a bag
I don't have material myself but you can often get Cordura in a variety of weights from fabric stores. Here in the DC area, there's a place called G Street Fabrics that carries a good selection of outdoor-style materials.
If the outdoor store sews stuff regularly, they might have access to the cordura and foam that would be required to add another bottle holder to your TEAM Bag.
Also, I'll see what we can do about creating an add-on bottle holder. Maybe we can create something that attaches using the small utility pocket next to the water bottle holder. Might be a nice option for anyone who want to carry two bottles...