- You may be looking for the real world publishers.
Obverse Books (PROSE: Contributors) later known as Obverse MegaText Conglomerate in the City of the Saved, (PROSE: More Tales of the City linking material) was a small publisher in the 21st century responsible for publishing Faction Paradox, Tales of the City, (PROSE: Contributors) and a "stupendous tome" about Iris Wildthyme and Panda. Panda believed the publishers to be a bunch of amateurs. (PROSE: Letter from the Editor) Obverse Books also had a sub-range of books called "Obverse Quarterly" in which the anthology Tales of the City was a part of. (PROSE: Contributors)
In the 21st century
Obverse Books published the anthology Tales of the City in their Obverse Quarterly range. The book was by Philip Purser-Hallard, and had stories by Juliet Kemp and Elizabeth Evershed. Elizabeth's story was The Socratic Problem, which was also her first short story that she had written. Philip Purser-Hallard had also written fifteen other short stories for Obverse Books. (PROSE: Contributors)
For a "stupendous tome" that they created about him and Iris, they hired Panda to edit it. Panda got through an entire box of red pencils editing it, in exchange for a case of gin, which he seemingly never received. The cover of this tome was also a photograph of him and Iris, though Panda was admittedly nude on the cover but he thought people would have their attention diverted by Iris' impression of Worzel Gummidge's sister. Panda had also written an introduction to the tome in which he wrote about all of this. (PROSE: Letter from the Editor)
In the City of the Saved
to be added
Behind the scenes
While not mentioned in PROSE: Contributors, authors Alan Taylor, Cate Gardner, Daniel Ribot, Kelly Hale, Stephen Marley (or rather Gladys Trubshaw in-universe), Helen Angove, James Worrad, Simon Bucher-Jones, Jonathan Dennis, Aditya Bidikar, Sarah Hadley, and Jay Eales have all written for Obverse Books in the real world.
Similarly, PROSE: Party Fears Two features Cody Quijano-Schell, Kelly Hale, Cavan Scott, Stuart Douglas, Jay Eales, Lawrence Burton, Paul Magrs, Philip Purser-Hallard, and Philip Marsh, but doesn't identify them as having worked for Obverse Books (though it is implied by their gathered presence).
Additionally, the short story A Hundred Words from a Civil War, the anthologies A Romance in Twelve Parts and Iris Wildthyme and the Celestial Omnibus, and the novellas Nursery Politics and Predating the Predators all exist in-universe, but again, they have not mentioned to have been published by Obverse Books.