iBook G4 Charger not working

Hello, I have a iBook G4 running OS X 10.5.6. When I first got the computer, the charger worked fine.

It was not the original apple charger. Then it would not start charging I had to put a lot of pressure just to make it charge. It was annoying so I used my sisters PowerBook G4 Charger to charge it, and it worked fine. This was the real apple charger. If I need a new one, where can I get a brand new one??

Thank you for Your help!

PS I just upgraded to leopard could that be the problem?