Cool, this might help, the 5v points are circled in Yellow and the 3.3v points are circled in purple. The vias can fit size 24 AWG wire and you can get a breakout for a USB socket for a few bucks from Sparkfun.com
I already have enough sacrificial USB cables to add a charging point.
According to the pinout I have, pin 35 (top) and pin 29 (bottom) are both 5VDC.
I'll check them with a meter first but will only take a couple of minutes to solder on a USB socket.