A v1 seems most likely (I'd guess that support still has v2 PSU spares worldside). Assuming a v1, I think the SeaSonic 250 watt sfx supplies are the ones you want. But you will need to modify ATX pinout on the supply. Here's a link: http://www.readynas.com/download/archive/pdf/ReadyNAS_PSU_pinout.pdf
Though it's ugly, you can also get a cheaper ATX supply and keep it outside the unit (since it won't fit). You might need cable extensions in that case (and you could then modify the extension cable instead of the supply itself). Probably not a good long term solution, but if the goal is simply to offload the files on the NAS then it might work.
If you are referring to the NV+ v1 that has 4.1.x FW version, support center in Australia ran of stock of this power supply unit already and will no longer restock it because this unit reached EOL status a long time ago. By the way, RND4PSU1 is the model number of the power supply in case you try to look for it online, there is a chance of getting one from online resellers.
Going through the same pain myself. I just ordered one from the UK here: http://www.evercase.co.uk/PowerSupplyUnits.htm#ReadyNASPSU. It's listed as compatible and after I ordered it I saw this same link listed in another similar post.
Yeah, will I have what I thought was safe data. I really only get one shot at this and so I'm willing to pay extra to make sure it has the maximum chance of success.
