I know what an AT PSU is. Just buy another one off eBay; there are plensitch? The latter is available onty there. Otherwise, bypass the switch. I doubt you will find the switch that you want for less than the cost of a PSU.
PS - do you mean the switch in the PSU itself or the case switch? The latter is available on eBay for less than a fiver.
I did not think about Ebay for the switch, thanks for that, as you said there is one on there for just under a fiver, I will have to ask my mate, as you said we could bypass the switch and turn of and on at the mains. It is the case switch.
I thought of something last night in that i have not really seen this switch as it is properly, I just had a peak at it and it looks like it is just pressed in, but Maybe the mount it is on is broken, I will have to take a proper look next week. Thankfully the machine have not been required for a while, but he wants to get it back up and running as it is required soon.
Desktop machine now powered by windows 8.1 pro 64bit, no dreaded metro, laptop by Linux