Fail power supply RND4000v3

The Flex ATX (aka mini ITX) supply is the right size for internal replacement (150 x 80 x 40 mm). They are common supplies for 1-up rack mount devices and some small form factor desktops.  You'll want to get one that has only one 12V bus with at least 7A so that you have sufficient 12V for the 4 drives.  Most 150W to 200W supplies will have that.  Anything 250W and above will likely have two 12V busses.  You cannot buy one with two 12V busses and tie them together, it won't regulate properly.  You can either pull and swap the pins or cut and splice the wires.  The 2x2 connector for CPU power has the necessary extra 12V wires.   A set of tweezers will work in a pinch to help in removing the pins.  If you were doing it often, you'd want the tool made for it, but tweezers worked for me to hold down the locking tabs for a one-time thing.  A couple of jewler's screwdrivers might work, too.

Note that some HP server versions use yet another pin-out and additional pin swaps would be needed with one of them.  Dell uses a mini version of the connector, but most supplies have the standard and an adapter.

I saw a few on eBay.au, though they do ship from the USA.