Parts-people.com is usually a good source but shows no stock of boards. Try EBay.  
I have a Dell XPS 15 9500 laptop. The warranty expired in March 2022. Its motherboard crashed in July 2022. In any case, this model has been the most faulty laptop I have used with poor design (laptop lid constantly shakes), and heating issues. I am trying to find a replacement for the motherboard which Dell customer care said is not in stock. I am totally stuck with this laptop which has/had premium price tag. Any suggestion on how to get a replacement motherboard and get this piece of really poor quality laptop functional so that I can transfer data from its ssd and shift to a new laptop?
Dell XPS 15 9500 Motherboard crashed