in a search engine site or 2nd hand site's search engine type :
part model number, (which should be on it) OR computer model number part's name
you can add to the search : new or genuine
I think it is prefered if the seller has a high feedback rate (above 3000)
![:elephant: 🐘](https://cdn.jsdelivr.net/emojione/assets/png/1f418.png?v=2.2.7)