I like this product.
“This is a set of medicine bags that fit right behind the cantle of your saddle making them very accessible when doctoring. They have two 500cc bottle holders as well as six needle holders. They also have two pockets on the side of the bottle holders for your marking paste or syringe holder. I had these made so you could pull medicine from either side of the bottle holders. You can see the wholes on either end of the bottle holder. These are great to use with saddle bags or saddle pockets by keeping your medical supplies out of the way when getting in your saddle bags. They can also be removed easily without removing your saddle bags.”
You can order it here: http://www.ranchworldads.com/classified.php?listing=12304