Well, not replacement fans, but a replacement case: I bought the Akasa Turing fanless case [0] for my NUC and couldn't be happier. I like the new looks, too.

[0] https://www.anandtech.com/show/16191/akasa-turing-fanless-ca...

Got a replacement fan from Ebay from a seller in China, replacing the fan was a little bit harder than the youtube tutorials but it worked in the end.

I used my nuc as a server 24/7 for an year before the fan started failing and now it works just as fine as before.

I use a NUC as an HTPC, and benefited a lot from tweaking the fan settings in the BIOS.

I got it to the point where it's silent when watching a movie or something, and only noisy when under real load.

The default fan settings of those nucs are dumb.

You want to set the cpu total power draw a bit lower, the fan onset temp lower (i know, sounds paradoxical) and the ramp rate in %fan/degree lower.

This means:

- cpu runs less hot at some performance hit. You'd have to be able to live with that. Maybe this works without reducing power draw (I'm neurotical about components getting too hot so I happily accept that)

- fan starts spinning sooner, but slowly, before things get too hot

- fan doesn't abruptly start making noise upon heat increase

Mess about with the fan profile in the BIOS. That's what I did and you can make it less loud.