3 Pack of Spark Glow Fob - Clear Plastic with M Green Tritium SPARK-001-3PK-G 

The Sparks Glow Fob features a powerful little device to help locate your gear quickly in the dark. The Spark Glow FOB features a 3-pack of Green Cylindrical Tritium Lamp/unit encased in an injection-molded polycarbonate casing with a glass breaker tip. The Tritium is what triggers this powerful light. It is self-luminous, and all that it requires is it to be dark. The spark will glow for over a decade. So connect it to anything you need to find quickly in the dark, like a keychain, lanyard loop, or zippers on your bag. Great for camping. It is waterproof and small enough that it doesn't impact the limited space that you might have. Its dimension is .0825" in length and 0.31" in diameter.