If it is such a low-power PC you could try a pico-PSU. Maybe you can score one for $40 off eBay. There might actually be a whole range of PSU one could get used for cheap.
Considering the troubles I've had with new PSUs, I hardly want to try a second-hand one with no warranty. At least I can send the new ones back if they're no good but I'm hopeful someone makes a decent, reliable, lowish-power PSU (not that I care about it being low power, just I don't want to waste money on power I don't need).
I tried a pico-PSU type (it actually had more current which I needed) a while ago and it ended up destroying about three hard drives in a row until I realised it must be the cause, I guess due to supplying insufficient power to the drive and that causing it to do strange things to itself, so I'm not going near those again, at least not on a system with HDDs.