Upgrading iBooks Airport Card

I want to upgrade the Airport Card on my iBook Clamshell can i buy a compatible Airport card from Apple? Are there any compatible cards that i can buy elsewhere? I really want to get this computer running as well as I can and its inablitity to connect wifi due to the poor Airport card is really bugging me. Basically I want to know if there is a way to make it connect to wifi sort of using a external Airport system.