The NRG Rechargeable Battery kit from Black Diamond converts your ICON headlamp to a rechargeable powerhouse.  The kit comes complete with everything you need for a "plug & play" conversion. 

The battery pack simply replaces your standard batteries (ICON has a plug for the kit in the battery compartment).  No need for an external power pack.  The kit includes the rechargeable battery pack, a wall adapter, and 4 plug adapters to allow for use in the US, Europe, Australia / New Zealand, UK, Hong Kong, China, Singapore or any other location using the same outlet configurations. 

Comes with a 3 year warranty.  Compatible with the ICON headlamp or Apollo Lantern.  Retail $29.95.