Have you attempted to repair the motherboard, As I have a broken asus fx705g too.
took it to a repair center and they are working on repairing it
If you still want to order a new motherboard here you go:
https://www.ebay.com/itm/324206140388?hash=item4b7c311be4:g:YfoAAOSwOOlgrNHo&amdata=enc%3AAQAHAAAA8BBWEW4B3JGZpmv4qM5TfHzJKG20dni7EsPyz96R2DYfJRPNusi86k32tkkMnEX%2BBkChkEAJVI%2Bv6n7xC%2BUqKV5fKAbxJae3nNg%2BkpBDCav4gtHw%2Fca%2Fi%2BxVb7Oiy4XFqxzmtcUQOXIA2hB%2BQKmTANO43fVf7ulH6NPIyC6MRvoh7%2Fv35P216pM0Xv79RxIjc0yJ4yy2kactbOSd4qdeIF393oe%2Bec0JPu6idVDEILHjs2MgeQJiu6PZnRGjswwPv1ed1TDaEM%2FxodKYiTQs%2BJaZ3hQTFb0EG4wjkP2POOMVZRGczKeH2TmYigxslTtrww%3D%3D%7Ctkp%3ABFBM_PHo2b5g