Currently there are 16 native Wideangle Prime lenses for Sony A900 and 9 of these lenses are autofocus (AF) type.
A900 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on A900.
Since Sony A900 has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 1 Wideangle Prime lenses with Weather Sealings.