During training I use a Camelbak fannypack type thing that holds water or what ever I want to put in the bladder. It also has a zipper pocket and I carry a cellphone, lip balm and granola bar.
During a race (I'm a walker, by the way, so I am usually out there longer than most runners) I wear a small fanny pack to carry my camera, cellphone,lip balm, gels.
If you have certain thing you NEED to carry, you may have to carry a fanny pack or get a small pocket type thing with a belt clip to go on your waist band of your shorts. I would try to get something soon, so you can at least do a trial run with it to make sure it works and doesn't rub in weird places.
I don't bring along water with me, the races are pretty good about having water along the way. If you aren't use to drinking along the way, just be careful with choosing water or the sports drinks. I switch between the two to avoid my stomack getting upset.
Good Luck at your Half Marathon.