Are you looking for a Battery Operated Beacon?
June 28, 2016
This Battery Operated LED Emergency Beacon is shock resistant, waterproof and durable.
The unit is magnetic, allowing it to be attached to metal surfaces, and can be recharged using a 12V car charger or a 230V wall charger:
http://beaconlamps.com/products/visual-warning-signals/battery-beacons/
Available in:
Red, Amber, Green, Blue, Clear and Yellow