Happy Bread in Pompeii Day, to those who celebrate.
(I have not checked CIL to confirm the citation / the original Latin. But at least this meme includes a source, which is promising.)
I can't access the physical volume, but sadly the major databases (AGP, EDR, EDBCS) don't seem to have this precisely.
4.8792 seems to document one grouping of the many graffiti from the "campus ad amphitheatrum" (Grande Palestra = II.7.1), which is often confused with the so-called "Gladiators' Barracks" (Quadriportico del Teatro = VIII.7.16), but no bread: http://ancientgraffiti.org/Graffiti/results?global=8792&sort_by=relevance
Here's everything the AGP has from Pompeii and Herculaneum on bread: http://ancientgraffiti.org/Graffiti/results?global=bread&sort_by=relevance