The picture shows the C13 AC-plug as included. This lead me to think, that something like Rewireable C13 plug is included.
But the clip is meant on that place, instead:
This lead me to contact my reseller about that.
I would propose to remove or gray-out the C13 plug from picture or remove that hint from the docs to avoid confusions.
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For folks who is confused like me:
The power cord is the same as on common PCs, Printers and co. and fits perfectly with retainer clip. So you do not want to buy one if you have one from your old PC.
Or you can buy it on each appliances near by shop.