Currently there are 15 native Telephoto Prime lenses for Pentax K-7 and 9 of these lenses are autofocus (AF) type.
K-7 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on K-7.
Since Pentax K-7 has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 3 Telephoto Prime lenses with Weather Sealings.