I think you will need to send it to Asus Repair. 2nd choice search eBay but you will be taking your chances in the long run it might be cheaper to just send it to Asus Repair.
I goggled this look like they seem to have parts, I don't see the MB it might be worth contacting them perhaps?
http://www.asusparts.eu/partfinder/Asus/Notebook/G%20Series/G46VW
G752VY-DH72 Win 10 Pro
512 GB M.2 Samsung 960 Pro
1 TB Samsung 850 pro 2.5 format
980m GTX 4 GB
32GB DDR 4 Standard RAM
Z97 PRO WiFi I7 4790K
Windows 10 Pro
Z97 -A
Windows 10 Pro