old Mini's can be found in karachi - after a lil search, Tariq Road, Saddar/Luck Star and Tower area.
More than the Kid's wish, Love the way to are aiming to his words.
BTW: the kids at this age make silly requests, no need to be that serious - let him grow like 15 above then going by the words is more meaning full.
Just my 2cents - as being a father like you.
God Bless us all with our Healthy Families.