Not sure which lock to get

Checking around, it seems that IWC discontinued this lock. It's best to try to use the 90-313 sash lock and re-mount 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, though. You could damage the frame or the glass in the sash. Sometimes it is best to contact a repair professional when you're drilling close to glass.