Hi,
I have the same printer. This posted article shows how to replace the print but it can be used for removing and cleaning the print head. I had to clean the print head and I used moistened Q-tips to clean the head and the electrical contacts. I then followed that up by using isopropyl alcohol on Q-Tips. It fixed my print head failure problem. Additional information can be found in this manual.
If you need a new print head then try eBay. Otherwise, I recommend that you buy a new printer. I have already replaced my printer under warranty and my neighbor had to replace his C309g since it failed off warranty.