Q: Where can I find a Quicksilver G4 power supply for cheap?

Check with local Mac usergroups.  Some have reclamation centers.

According to www.welovemacs.com, those power supplies are simply not made anymore, so finding a truly cheap one may be a real challenge, especially just online searching (like everything, once they get scarce, they get expensive).

Along with a brody's idea, you could also try posting a WTB item on some other Mac forums that have classified sections.  Macrumors does not have a classifieds, but they have a collectors forum.

I see them here - http://resale.headgap.com/g4powersupply/ but not cheap.

You can convert an ATX PSU for use on a G4...

http://atxg4.com/sawtooth.html

http://atxg4.com/gige-da.html

http://atxg4.com/quicksilver.html

http://atxg4.com/mdd.html

http://atxg4.com/