Ebay is all I can think of. Unless you happene to know someone who has a copy they are willing to loan you.
That being said, I was unaware that there was a difference between the versions in regards to the G3 and G4. I know that my copies came on a CD and a DVD (CD version doesn't install iDVD and GarageBand), but I've installed it on my G3 iBook and my G5 tower, so you shouldn't have any problems.