Hi hector 911. I have never heard of a power supply with an external 12V output socket. If you or someone you know is competent with a sldering iron and electronic components, then I would suggest taking an output from the 12V P4 connector that all ATX power supplies have these days, and feeding that via a suitably rated fuse to a connector at the back of the computer case. You should be able to find all the components you need at Maplin click here. But because of the amount of power available from an ATX power supply, this must be done by someone who is familiar with this kind of work.