Try calling this builder. They posted a photo on Houzz with these vents.

AC Pros make them call them

• Serving Tarzana and surrounding area18653 Ventura Blvd
  Ste 251
  Tarzana, CA 91356Tarzana
• Phone number(818) 342-7767

These are used a lot in commercial applications. Our new build is not very large so rather than go with something oversized, I found some in standard a/c duct sizes. They are called linear slot diffusers. Here is a link to a 48" from this company the company that I hot the standard size from:

https://www.amazon.com/dp/B06XQ8JL9V/ref=asc_df_B06XQ8JL9V5397839/?tag=hyprod-20&creative=395033&creativeASIN=B06XQ8JL9V&linkCode=df0&hvadid=198099432697&hvpos=1o1&hvnetw=g&hvrand=9784463738137180546&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9031020&hvtargid=pla-367393111903

pardon my typos, typing on my phone with my fat thumbs.

The vents you are showing are linear slot diffusers and have a plaster in place trim. Meaning the trim piece is installed before the plaster or drywall are finished. When the plaster / drywall is finished the mud covers the trim piece and gives you the very clean lines you are seeing in your picture.

Above these tiny slot diffusers is a very large plenum box which takes up quite a bit of space, much more than standard hvac vents do. I would do a little bit of research on plaster in place trim slot diffusers and the associated plenum boxes that go with them. They will be a high end option.