A lot of knock off ones but they do work pretty well. If you do want a real Sony one yes hard to find. Some links to help you out.
http://www.laptop-ac-power-adapters.com/sony-vaio-pcg-61317l-replacement-ac-adapter.htm
http://www.laptop-power-adapters.com/sony-vaio-pcg-61317l-laptop-ac-power-adapter.htm
http://www.laptop-ac-power-adapters.com/sony-vaio-pcg-61317l-replacement-ac-adapter.htm
https://askleo.com/can_i_use_a_power_supply_with_a_higher_wattage_rating_on_my_laptop/
http://www.laptop-ac-power-adapters.com/sony-vaio-pcg-61317l-replacement-ac-adapter.htm
http://www.laptop-power-adapters.com/sony-vaio-pcg-61317l-laptop-ac-power-adapter.htm
http://www.laptop-ac-power-adapters.com/sony-vaio-pcg-61317l-replacement-ac-adapter.htm
https://askleo.com/can_i_use_a_power_supply_with_a_higher_wattage_rating_on_my_laptop/