We have been using the Sony PMW-EX3 for a number of studio projects. The power supply provided is a little awkward for constant use when the camera is a studio camera, I thus looked for alternatives.
At 12V the EX3 takes around 0.9 Amp. The XP Power 12 V 15 W device ( XP POWER - AEL15US12 - PSU from Farnell ) does a good job and is cost effective and small.
You will need the correct connector, an MP 204 - from here (Farnell) outer connector must be wired negative!