Some links for you to check out - https://www.modernironconceptsnashville.com/

http://www.chapmaniron.com/site/index.php

https://www.custommade.com/gallery/custom-railings/

https://www.lowes.com/pl/Stair-railing-kits-Interior-railings-stair-parts-Stairs-railings-Building-supplies/4294512334

https://www.stairsupplies.com/product-category/wrought-iron-balusters/

Make sure your designer is talented enough to make things look good within the parameters of the building code, please. Anybody can draw cool looking stuff.

We had railings like that made by an ironworker and powder-coated. Not overly expensive.

Depending on how minimalistic you're looking as well as how similar to the images you've provided you want to get your look, you may want to look at the Wagner Companies - Railing Systems Catalog starting around page 160 or so?

Also, I would reiterate the building code comments as the second image you provided looks almost too minimalistic that I'd question stability and application. Maybe a hybrid solution would suffice to full-fill your visual appearance, function and railing system building code requirements?

Side Note: I do like the two steel stair railing options you gave as examples as they look very "crisp & clean".