Have you tried looking at Aquatic suppliers ? The size and shape look rather similar to those used in a water feature
This one is quite close. If you do a Google image search for metal/corten steel fire bowls you’ll get more options
Or there’s this which is plastic, much cheaper and out of stock. I expect there are other stockists. A Google image search or Tin Eye reverse image search will help.
Third edit to say I think it could be this one. That it has a RRP suggests others might stock it too