Where to get 128GB SSD like the one found in Macbook Air (late 2010 model)

Ok so I am using a Macbook Air (late 2010 model). I purchased it in Dec 2010 and simply loved it until a couple of days ago when suddenly it froze while I was working and when I restarted it, it does nothing but starts up with a chime and a white screen of death (no apple logo).

And it has been like that since then. Unfortunately it is out of warranty.

A friend of mine (who is techy enough) unscrewed it and planted SSD from his Macbook and it booted up fine. So the simple thing is, I need a new SSD.

But I am having trouble here in Pakistan because we don't have an official store.

What would be the best possible way to purchase this spare part online? Please help.