wow that baby is some custom psu.
Trotter is right HP or ebay will be your best bets.
Here is one where I found a pic of it.
HP Compaq d530 USDT Power Supply ( HP-L1520F3P ) (item 32427344) - Lelong.com.my
Also for updating the gpu, there is not pci-e slot on that board. You also need a low profile short card to fit in that case. It may not be in the cards for him and it might be better to save the money for something else ie new build.
He will probably spend around $150 and that is a third of the way to a pretty nice new build.