Seasonic does. They make excellent power supplies. I've used a 400w fanless in a media center PC, but they also make higher wattage units like this for example: https://seasonic.com/prime-titanium-fanless
A higher wattage than 400W is utterly pointless for a fanless PSU; if you need to dissipate constant loads of >400W of heat, you will need a fan somewhere (exotic options like mineral oil cooling aside).
Well you can always add absurd amounts of surface area and mass to the heat sinks to take advantage of thermal inertia, or possibly change components to simply raise your safe operating temperatures to absurd levels. But that's pretty involved. Spacecraft take care of huge temperatures with no fans or even conductive or convective cooling. But that requires enormous, sail-sized surfaces to take advantage of extremely slow radiative cooling.
It would be an exotic option for sure. And not something you'll find pre-built.
Wow. That thing has more surface area than a motorcycle engine. I guess it really needs it with such a relatively low temperature gradient, not to mention the absence of airflow from movement. I'd love to see how that really performs.
I have a Seasonic Platinum X-400 fanless, but I'm quite disappointed because mine suffers from quite loud coil whine noise that is more annoying to me than a fan would have been.