Camera Bags come in all shapes and sizes and are all designed for both the type of camera and the style of photography undertaken. For instance, a casual photographer may just require a simple small bag to carry their camera in during trips away. The more professional photographer may require a bag which can carry everything but the kitchen sink.
Also the condition that the camera may be used in also has to be considered. If you are likely to be out in all weathers and require your bag to be ultra water proof and secure then a specialist rucksack may be the answer.
Check out these bags on Ebay and see if you can find the right one for you. If you cannot find what you are looking for type in the search box to search for other items.