Well i don't know if already posted here or somewhere else but i will post it.
I found it when i "played" with my "Frankenstein" psp.
You bored to see the yellow plastic when you hold your psp ?
Do you want a cool led in the yellow plastic's case while you hold your psp ?
Then just solder two cables in the places that arrows shows. ;)
Here is a video that i found which it seems that someone already done this so you can see how it looks.