Welcome!
"Where can I get ...." questions are hard to handle here without our knowing your approximate wherabouts. These are world-wide English-language forums so it does you little good if we recommend a source that is a 3000km drive away, or does not ship to your part of the world.
If you are in the US or Canada, consider PowerBook Medic. They have maintained stocks of used/pulled part for old Macs for a long time. Admittedly, COVID seems to reduced their inventory for some model but it is certainly worth a try. I kept a friend's three G3 PowerBook "Wallstreets" in working order far past their "use-by" dates with PBM's help.
TIP: PowerBook Medic's model listings often use Apple's arcane "order numbers" (like "M8582LL/A ") to identify Apple computers. The only place you can usually find your order number is on a sticker on the shipping package, which I'm guessing you no longer have. The best research tool for working with those designators is free, easy to use, and in the Mac App Store: the MacTracker database. There are versions that run on macOS, iOS and iPadOS.
Good luck! I too love keeping old Macs serviceable.