many stalls, shops and pasar malam stalls sell lightning cable. The only thing to look out for is that only official Apple and Apple-certified 3rd-party lightning cables (those with MFI certification) will work (both data syncing & battery charging) fully.
with iOS 7, many of the cheap 3rd-party cables simply will not charge with devices on (or rather iOS won't allow the devices to be charged). You will very clearly notice this when you get the prompt.
A friendly advice: some of the cheap lightning cables with blinking LED lights are blindingly bright and extremely distracting, avoid them like plagues, please.