The Virginia Museum of fine art which has a few artifacts from this building also has at least one of these lunettes with a very similar design on it as the spandrel panels have.
I like the shape of it as well, I have no plans to but easily could make the surrounding flat pieces for it if a client wanted them.
I will be working on this model very soon, of course it takes time and this type of work is done when I have time, and more time for the various mold making processes to get done, but progress photos will come along here soon enough.
This would most likely be priced around $325 in fired red terracotta.
The museum has their artifact sized 18-1/4″ x 18-1/2″ and 4″ deep, this size would fit into my existing kiln, so this is another design I can keep my model of full sized like the originals and offer both interior cast-stone this size but less deep to hang ON the wall, and hand-pressed terracotta which will be slightly smaller due to the shrinkage of the clay but made a nominal 3″ deep which can be additionally used outdoors in the garden or embedded into a brick or stone wall of any type.
Dankmar Adler, 1844-1900
Louis Sullivan, American, 1856 – 1924 (Architects) Northwestern Terra Cotta Co., probably modeled by, Kristian Schneider 1884-1885
A photo of the grey painted artifact in the museum which is not on public view at the museum, appears here; https://www.vmfa.museum/piction/6027262-7946023/
The artifact they have is a gift of the Metropolitan Museum of Art.