where can I buy a motherboard of my note 4? My motherboard is defective and needs to be replace. I bought my note 4 from Singapore 2 yrs ago. thanks for your help.

Hi.. I need help. where can I order a motherboard of my Note 4? I need to replace it coz its defective. I bought my Note 4 from Singapore. And what are the serial numbers that I need to take note before I order a motherboard so that it would be compatible of my Note 4 that I bought from Singapore. Please comment. Thanks for your help guys.