I and others
barked up this ally a year ago...as many others have.
Martin (IIS user MILL) found this neat little switchmode unit that can be made into a camera PSU.
Easy to make into a camera battery...just buy a cheap fleabay DSLR battery cut it open tear it's internals out and wire up.
The only Issue I had was that my Canon DSLR battery has 3 terminals, +ve, -ve and one that reports "charge". I didn't wire in this "charge terminal" so it reports 30% cell charge all the time. Not a big problem though as it's a PSU not a cell.
That said when I tore apart the battery it had a small cctbrd and I could have wired up the "charge" terminal...just got lazy.