How old is the camera? If it's under warranty, get it replaced. try the manufacturer anyway, they probably sell spares as this is a common fault on most cameras. If the door is plastic, superglue will probably work, but give it 24 hours to harden properly before putting any strain on it (eg closing the door). Failing that , use The Force! (aka gaffa tape; it has a Dark side and a Light side, and it holds the universe together!)
Tim