Currently there are 15 native Telephoto Prime lenses for Pentax K-70 and 9 of these lenses are autofocus (AF) type.
K-70 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on K-70.
Since Pentax K-70 has environmental sealings (Weather Sealing), you may like to couple your camera with one of these 3 Telephoto Prime lenses with Weather Sealings.