wow, they really are interesting. I would think that steel would rust too quickly, so they must be aluminum or stainless steel.

maybe drive through you local industrial park until you come upon a sheet metal shop, and show him the picture. I suspect that would be you least expensive option.

I've seen similar planters made of steel. The rust actually makes for a pretty neat effect, as shown below.



I'm sure there are many professionals on Houzz that could point you in the right direction.

I saw this photo recently. Just checked the questions and the designer who posted the photo responded to someone who was looking for the planters. The designer said "You would need to have a local steel fabricator make them out of 1/4" steel. Ask around as prices can really vary. "

Find your local steel fabricator in town. They should be able to help.