This MFJ-4103 Miniature Switching Power Supply can deliver up to 40 Watts (13.8 VDC at 2.89 Amps) of reliable power anywhere in the world! It's an incredibly tiny 4 1/8 x 2 5/8 x 1 3/8 inches and weighs just 10 ounces including output power cord and connector.
It has an output DC cable with a standard MFJ coaxial DC power connector (2.1mm ID, 5.5mm OD) that fits most MFJ and other ham accessories and QRP rigs. A sturdy adapter cable is also included for use with the Yaesu FT-817ND.