Good news bro, i found a shop that has the exchange able covers .. there's a nokia care shop in main zamzama, right next to the Home Shopping Network outlet. They have a ton of Lumia related shit there that I haven't seen anywhere in karachi, branded pouches, official covers and back covers for all the lumia models that allow the back cover to be changed.
I bought one red and one cyan, replaced the default with cyan, it looks soooooooooo slick !!
the only downside is that each cover is 850/-rs a pop, a bit steep imo but whatever.
took this just now.