Hope you haven't thrown it away yet!
Just out on a limb here, but if you tried using a PC ATX power supply, it may not turn on because it might use a different way of triggering power on through the ATX power connector to the mainboard. In other words, the motherboard 24pin ATX connector might not have the same pin-out as the Quicksilver's original PSU.
"The Power Mac G4 MDD Used a uniquely shaped 344W or 400W AcBel or Samsung Power Supply. It had a 24-Pin Connector (not 24-Pin ATX!)" See
https://www.ifixit.com/Guide/Power+Mac+G4+MDD+Power+Supply+Replacement/1622(I know you do not have a G4 MDD but the principle is the same)
I would recommend ordering a replacement PSU off eBay or a mac parts reseller that supplies older parts. Maybe someone here on the forums has a spare PSU you could buy?
Don't throw it out yet! It seems to have a 1 GHZ dual processor! That sounds like a great second hand machine.