I've been all through the HP web site, including their spare parts system, and I've talked to HP help desk folks until my ear feels like detaching. No help. They claim that the switch itself is not replaceable, and that we have to get a new case.
It seems downright silly to buy a new case and go to all that trouble of relocating all the parts just because of a $10 switch.
The other problem is that my parents live about 200 miles away from me, and I don't have the system sitting in front of me. So I'm going by my memory of their system and the one attached .jpg I was able to find on the net. It's the big power button in the middle of the front panel.
Will any ATX power switch do? Any recommendations as to which vendor to use?