locating ibook serial number

SeePowerPC-Based Mac notebooks: Identifying the right power adapter and power cord--US and just find the description that matches your iBook and the appropriate power supply.

See if your iBook is listed in this article. It avoids the dead links in the other:

iBook (Dual USB) and later: How to find the Serial Number

However, check out this item:

http://eshop.macsales.com/item/NewerTech/APLPBI65W/

Look at the compatibility chart. It suggests that charger is compatible with most G4 (white case) iBooks.

Note: Apple no longer sells the chargers so you are shopping for either a used item or a third-party item like I linked.