Small (thin) power supply needed recommendations?

I am making a low power file server. I'm using a C3 chip and micro ATX board with the goal of keeping this thing super small. The side affect of this is that traditional boxy power supplies don't fit. 1U rackmount powersupplies come the closest but they are still big for what I need. I'm trying to see if anyone knows of a powersupply that is about 5x3x1.5 inches or so. I definitely want it thinner that 2 inches if possible. Since this is a lo power file server I think I can get away with 90watts but cost isn't really my concern here. On a side note, how important is an ATX powersupply, I mean if I can build a good supply that outputs the 12, 5, and 3.3 volts could I use it instead of haveing the fancy power on logic from a ATX supply?

Jason