The ATX breakout board bench power supply is back in stock at Seeed Studio. This board recycles an old computer PSU into a handy bench tool with 3.3/5/12/-12 volt supplies.
You can get one for $14 at Seeed Studio.
You can also get a Sick of Beige case for your ATX breakout board for $4 at Seeed.
I am wondering what is the current rating of the ON/OFF switch?
Not much, but it is only the trigger that turns on the PSU, no large currents flow through it.