Need help replacing my broken window lock

The IWC sash lock that you show in your photo is no longer available. They suggest using the 90-313 sash lock and remounting the holes at the top. You will need to use a screw similar to the 33-011. You don't want to use too long of a screw or drill too deep, because you could damage the frame or the glass in the sash. See if this is something you can handle.