Toyota Motor Oil (TMO) can be found at every Toyota dealership in Pakistan.
In Karachi you can get it from Toyota Eastern Motors. I see many debate on the type of oil being best for a car here in Pakistan. well in Pakistan 20 W50 is better and cheaper option to use for 1300cc, 1600cc and 1800cc vehicles.
I would recommend Toyota Motor Oil PETRON (SL Multigrade) which costs 1900 Rs (4 ltr can).