What do to when there's no paper to jot notes down?

Some times there just doesn't seem to be enough paper when an idea comes, you know? Maybe you're driving down the road, a country road, and you see a beautiful field with wild flowers dancing in the wind and a lovely lake sparkly brightly in the light. Or, maybe you're at a stoplight and you see someone running across the street with two or three people hot on his/her heels. Little scenario like those can often spark an 'idea' moment that might find its way into your next piece. I know that happen with me and if there's no paper anywhere for me to jot it all down, I have to try my best to remember what I saw/heard until paper can be located. There are some people who use little voice recorders and use those as their pen and paper to help them remember what happened and use it at a later time. What do you use to help you in those 'idea' moments and there's no paper handy?