Just for the help of other pakwheelers: I went to all three/four shops in plaza's chaat wali gali for parts: i) Eastern, ii) Arafat, iii) Nippon. Arafat is apparently the cheapest, Eastern is somewhere mid way but will give 2-5% discount if you purchase a few items totaling more than 20-25k, and Nippon is the most expensive (at least in my view) with zero discount.
For local parts: Barkat autos which is the basement of the building on right side of magazine lane. once you enter magazine lane from the opposite direction of Preedy police station, you will see japan plastic and haram autos. Two shops after Haram Autos, there is a small lane on the right side which takes you in the building. First left and first right, you reach the stairs. You reach the basement and ask anybody for barkat autos. There you go !!