If your NV+ is less than three years old it should be under warranty. Open an on-line case with technical support.
You may also want to try Amazon.co.uk
. While the listing is in pounds and they ship free in the UK, they may ship to the rest of the EU and accept Euros.
Googling from Europe may also turn up other sources that are not showing up on my searches. the correct part number of RND4PSU1-1000s is shown on the Amazon listing. Just Google Netgear RND4PSU1-1000s and see what you get.
Remember - the NAS is not a backup plan.
Backup = Good, No Backup = Bad