You may find an authorized Apple service provider who can repair and help keep
an older vintage or obsolete computer running, but parts are generally a problem
for old vintage obsolete products. An independent Apple authorized agency that
does these may be found, when most Apple retailers handle much newer gear.
So if you cannot locate suitable correct parts, you may need to be looking for
other similar build model year identified vintage PowerBook G4s for parts.
This link may work to help locate sales, service, or other Apple related item, there:
https://locate.apple.com/
If that ^ page does not automatically show info on your country, see following link,
I found by looking deeper. You'd need to put your nearest City of size to see what
appears; in the Philippines you may find some areas have more or less results.
Click on the flag/name icon to open the link:
Philippines - sales, service, training, certification - Apple
Hopefully you can locate someone there who may be able to help.
Good luck & happy computing! 🙂