Where can I get an Apple PowerBook G4 replacement power hand over online?

If you haven't checked the apple website, that'd be my first stop.

You can try:

http://www.igo.com

Whether shall not be exactly the same, but you genuinely only need the correct electrical and end plug.

You could also search using google or yokel As well. I'm convinced there are alot of places to find what you're looking for.

Good luck!