Currently there are 15 native Telephoto Prime lenses for Pentax K10D and 9 of these lenses are autofocus (AF) type.
K10D also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on K10D.
Since Pentax K10D has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 3 Telephoto Prime lenses with Weather Sealings.