Get a water bottle that you like. Your bottle can be just as much a part of your outfit as your purse. Then take it with you. If you like looking at it, then you'll like having it around. AND it's easier to keep track of oz, when the size doesn't change. Mine is an orange Nalgene, with a yellow lid!
http://www.nalgene-outdoor.c
om/
http://www.kleank
anteen.com/