i used to just wrap the "supplies" in a paper towel and stick that in one of my cargo pockets. keeping them on me at all times meant no risk of anyone snooping and me not having to fetch stuff and carry it to the bathroom. if just sticking it in your pocket doesn't suit you, they make boxes and cases for that exact purpose. depending on what you use/how much you need, you could also use the box/case for something else (glasses case, food container, etc) to put them in.