Any reason you aren't running Linux on the laptop? Also, you might want to look into a used Macbook Pro. As you have seen, they can last for awhile and parts

Any reason you aren't running Linux on the laptop? Also, you might want to look into a used Macbook Pro. As you have seen, they can last for awhile and parts (like batteries) are usually easy to source even years after they've been discontinued. FYI, they stopped using the PowerBook naming in 2006.