installation disc.
This will be compatible with everything from that era.

Try to avoid the "grey colored" discs. These are the discs that came with a computer and are usually specific to the model they came with. They do not always work with another computer.

Another thing you have to be aware of is whether your Powerbook G4 has a CD drive or a DVD drive. I believe your model had a DVD drive but you can confirm that by looking at the details in "about this Mac/Computer" which you'll find under the Apple menu at the top left of the screen.

I note that eBay has a number of the Retail versions of 10.4 which should be suitable for your Powerbook

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