[ Desktops ] Open Question : Where can i buy a HP pavillion slimline power supply?

im looking for a better power supply for a HP PAVILION SLIMLINE it has to be a slim PSU or it wont fit, my case is 3.5" wide and about 14" long. ive looked EVERYWHERE and i cant find one, PLEASE HELP! PS: i want it more than 350w !!