I previously wrote a bit about how to order a power supply for your Xbox One because Microsoft makes it so convoluted that it’s worth blogging about.
Unfortunately, the complication does not end with finding how to do it. While I would still point to that as the only way to order a brand new original power supply from Microsoft, I would not recommend it to anyone. Long story short, 6 weeks and 3 support interactions later and Microsoft still hadn’t shipped my power supply, nor were they able to explain why they hadn’t and what the problem was.
So if you still want to get an OEM power supply, but don’t feel like waiting 6+ weeks for no reason, take to ebay. You might just find what you’re looking for.