Yep, after much headbanging on IRC with iMac600 and others, this was the conclusion we settled on. I have a box of 24V Powerbook supplies with dodgy cases I picked up at auction. I'm going to send him one, and install one on my DA.

Granted, it may not supply enough current to run an ADC display (4 amps!) but it should be enough to keep the logic board and a few powered Firewire devices happy.