I am a bit confused by your post, because the RND4000-100EUS has an internal supply, and you seem to be saying you have a unit with a brick.

Assuming it is an RND4000-100EUS (ReadyNAS NV+ v1):

First, it is worth checking your warranty status (warranty is 5 years for the original purchaser), since Netgear will provide a free one if you are covered. Also, if your ReadyNAS serial number is between 000DA2010FFE and 000DA2016000 then you are also entitled to a new PSU (due to a quite old service action from Netgear).

Assuming neither of those apply:

Replacement supplies are pretty scarce, and tend to be expensive..

http://www.amazon.com/NETGEAR-Spare-Power-Supply-Readynas/dp/B000W3X480

http://www.evercase.co.uk/PowerSupplyCompatibility.htm#Readynas

http://www.ep-mediastore-ab.de/netzteil-220w-readynas-nv-nv-1100-p-18023.html

It is possible to adapt a much cheaper ATX power supply, but it would have to live outside the chassis. Here's a thread that might help: https://community.netgear.com/t5/New-to-ReadyNAS/Replacement-Power-Supply-for-UK-NV/td-p/916501

Some folks have also tried purchasing an NV+ off of ebay, just to get the supply or other parts. For instance there is an active bid here: http://www.ebay.com/itm/Netgear-ReadyNAS-NV-4-TB-RND4000-100NAS-NAS-/281764338908?hash=item419a769cdc

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