Does it have to fit the case exactly or will you be making a hole to fit it?
If it's a normal ATX power switch, it needs to be momentary, single pole, and it would probably be a bonus if it fitted the hole vacated by the presumably faulty switch.
basically it's not going in a case, i want one to test mobos when they are not case mounted. all i need is one with the two pin connector for connection to the mobo.