What speed is the PowerBook G4? Is it an older, 400 or 500MHz model, or a newer, 1 GHz or faster? How much RAM does it already have?
You can get a power cord from a place like this:
http://www.powerbookmedic.com/Powerb...p-1-c-380.html
If the system is relatively speedy, then I'd go all out with Leopard, which can be ordered direct from Apple's online store. If it's an older, slower model, Tiger may suit it better -- you'll have to scrounge on eBay, Craigslist, or perhaps some online Mac stores (Powermax.com, baucomcomputers.com, etc.) may carry it. Be sure you get
retail disks of Tiger --
not the gray-colored, system-specific CDs/DVDs.