You can call Dell Parts and see if they have any in stock. Amazon between 75-150 . eBay has them from 50 - 150.also before I forget.5K7J8 500w Delta99TPH 500w LiteonY7R0X 500w ChiconyThose are the part numbers for the 500 watt psu's used in the xps 8940     
Can I put an Intel Arc A750 Limited Edition graphics card in my XPS 8940?
XPS 8940, compatible with Intel Arc A750 LE?