It's a 5-year old laptop, out of warranty, official ASUS parts would be expensive. Besides he didn't include the laptop's entire label (G771J?).
The model doesn't show up in the European market. But does show up in the Western Hemisphere, here's a link:
https://www.asus-accessories.com/If he was smart, he would use this site to identify part numbers needed then use the Internet to source the lowest price and availability.
With all the parts he requires (battery, SATA HD or SSD, M2 NVME SSD, memory) i suggested he consider the value of a 5-year old laptop versus a new laptop.
G752VSK, G75VW-3D, G51J, G1S
Homebuilt Windows Server