The little tiny ziplock plastic bags can be bought at any craft store, in a number of sizes. They're usually somewhere near the beads section, since that's what the crafty folk use them for. For each medcation, I insert a typed slip showing the name of the medication, the dosage and the expiration date.
While researching first aid supplies for my dog, I discovered veterinary wrap. It is a self-adhering wrap made of foam used for keeping bandages on the legs of dogs and other animals. With a few stiffening strips of duct tape on the outside, it will work fine as a sprained ankle bandage on a human (I tried it out). And it's far lighter than elastic bandage. It's available at any farm store. So here's another multi-purpose item–if you have a dog!
Re doggy first-aid: Aspirin (preferably the coated kind) is the painkiller of choice. Ask your veterinarian for the dosage for your dog. Acetaminophen (Tylenol) and ibuprofen are both toxic for dogs. All other first-aid items work for both dogs and humans, including Benadryl (useful should your dog snap at a bee or wasp instead of a fly) and Immodium. Again, ask your vet about the dosage. All this information came from my-daughter-the-veterinarian.