Thanks very much for that, but I realised that I forgot to say in my original post that I'm in the UK, so am looking for a UK-based supplier.
Compatible power adapters can be purchased through Amazon UK. Here is a search that displays those available: Amazon.co.uk: nuc power supply. Any of those that provide 19V 3.42A (65W) will be compatible.
Hope this helps,
Thank you very much, Scott - that's extremely helpful.