Waitasecond. A clamshell model? Those babies won't handle Leopard, and will only handle Tiger if you have a FireWire model. Even if it can handle Tiger, I'm not sure I'd put it on there - it would probably be very slow, almost unbearable to use. I'd keep it right where it is operating-system wise.
I would see if they can get you another AC adapter, just as a backup, especially considering that my own adapter that would go with a clamshell iBook recently started fraying and sparking. They're not very durable, so you may want to get another if you can.
Beyond that, your best bet would be software. I'm not sure how much hardware you could ever get for a clamshell, simply because of their age - Apple quit selling those models a good seven years ago, at least.