Where can I buy the front screen from?

the cost of replacing the screen on my nexus 5 is 80% the cost of a new device so i bought a new device. if i can personally replace the broken screen im sure it would cost much less. so my question is where can i buy the screen from? AND hoe do i replace it ?

P.S. i live in Saudi Arabia so i'm shipping the part anyway. either from the US or china.