You can buy these little gizmos at the plant shops. They're designed to be screwed onto the top of a soft drink bottle, which you fill with water and stick in the ground at the base of a plant to water it over a period of days. The tip has one tiny hole to allow the water to slowly bleed out. Cut off the tip of the orange gizmo as shown in the photo, and cut the bottom out of a plastic soft drink bottle, and you have along skinny funnel. While touring, you can stick the orange gizmo in your tool kit, and you will have the basis of a funnel if one is needed.