There are 3 potential materials for crafting such a surround.

Concrete: https://plankandpillow.com/five-ways-to-use-concrete-in-your-home/

Stone or Marble: https://ltwdesign.com/mercer-project-6-7m/

Steel: https://brandnerdesign.com/collections/housewares-and-accessories/coat-racks/ross-peak-great-room-guillotine-fireplace.html

In any case, it needs to be custom made from a non-combustible material in order to fit your space and be made flush around the fireplace opening.

You will need to find a fabricator that specializes in your material of choice.

I specialize in steel surrounds and ship them nationwide. Steel is much lighter and can be installed by a DIYer. Let me know if you want a quote.

I was thinking it looks like concrete but never considered steel for a fireplace. Wouldn't the heat conduction of metal be an issue with anything touching it?

The steel can be insulated, so it's not an issue.