This DIY project is a great way to re-use some old clothing (yours or your pup's) and create a custom treat bag that fits your needs!
DIY Dog Treat Bag tutorial http://terriesandelin.blogspot.com/2010/06/dog-treat-bag-tutorial.html
Citizen Canine - Dog treat bag / bait bag. Great for training class or walks. - TOM BIHN
This is the how-to description for how I made dog bait bags (treat bags you wear on your belt loop, used to train dogs) for the Humane Society.
to make: The Pocket Treat and Training Bag Photo
Chalk sac tutorial, could be nice for a camera lens too...
6 of the BEST Dog Treat Pouches - cute clutches to hold your keys, poop bags, and treats on dog walks
Dog treat bag sewing tutorial
Citizen Canine - Dog treat bag / bait bag with extra storage for phone, poop bags, etc. TOM BIHN $60