Ever since we built the cabin shown in my avatar, I've looked occasionally for a screen for the fireplace. It's the smallest all-masonry Rumford style one we could build. Dad cut and laid the stone himself, well into his 70s.
The opening is "over-square", taller than it is wide, about 24" x 30", so I couldn't find anything pre-made. I inventoried my skills and decided to make something myself.
It's made of 1/2" copper water pipe and fittings, with an 8 mesh bronze screen, and I cut out and hammered some copper oak leaf and acorn decorations for it.