Get the Scouts to create and hide their own geocaches.
Depends on what type of Cache you aim to create.
A container that is both Waterproof and hardwearing.
Paper logbook and pencil
An account on www.geocaching.com
After teaching the scouts about Geocaches and having found a few, get the scouts to create and hide their own caches. They can check them in the future to see how many people have found them.
Some Useful Links:
http://www.wikihow.com/Create-and-Hide-a-Geocache - step by step instructions.
https://www.geocaching.com/seek/default.aspx - has Geocache welcome notes in different languages.