Any way to add a new drive to an iphone 5?

Not that i have used my 16 gigs yet, but i was wondering if one could take apart the device and replace the drive and then back it up. If so where can i buy a hard drive that is compatible

Nope.

iPhones use flash memory (not a drive) that is soldered (welded) into the motherboard. And unlike many Android phones, they don't have a slot to add more memory.

I suppose you could unsolder the memory and solder in a bigger one, but I've never heard of anyone doing this, it likely would require undoing and redoing dozens or more teeny tiny delicate connections and you might need a microscope. It would be cheaper and easier to simply sell your current phone and buy one with more memory.