Posssibly take a cheap external drive cabinet's power, add a Y-adaptor, and see if that will power it. Way smaller if you retrofit the board into something more appealing. Just a thought, but micro-ATX may prove easier depending on what you are doing.
MacBook 2GHz Intel Core 2 Duo w/ 2GB DDR2 RAM & 120GB SATA 5400RPM HDD
Canon Rebel XTI
Google Cr-48 Beta Laptop