Personally, I like the idea of using the zippered bags that curtains come packaged in. I put five "quick kits" inside that have items generally needed for situations such as yours. The quick kits are in quart-sized zip-locks and are designed to be just pulled out and tossed to a person who needs one or who is helping. I also have other items in there besides the quick kits. I know the zippered bag isn't exactly the most robust carrier, but in a backpack or car-based case it should be fine.

My $.02