power supply (with SATA) replacement for Dell 400sc server

My Dell 400sc Poweredge Server has a 250 watt power supply without an off/on switch.  It's gone bad and I want to replace it with one that has SATA connectors so I can hot swap a SATA hard drive.  I think most power supplies would fit but they all have off/on switches and I'm not sure they would work with this computer.  Can someone comment on this, and also suggest a replacement power supply that has SATA connectors.

John