I wasn't familiar with this painting, for the very good reason that it doesn't exist
Are you sure? The wikipedia page on Flaubert's novel says: "In 1845, at age 24, Flaubert visited the Balbi Palace in Genoa, and was inspired by a painting of the same title, then attributed to Bruegel the Elder (now thought to be by one of his followers)." And the National Gallery seems to think they have it in the West Building (https://www.nga.gov/collection/art-object-page.41602.html).
Are you sure? The wikipedia page on Flaubert's novel says: "In 1845, at age 24, Flaubert visited the Balbi Palace in Genoa, and was inspired by a painting of the same title, then attributed to Bruegel the Elder (now thought to be by one of his followers)." And the National Gallery seems to think they have it in the West Building (https://www.nga.gov/collection/art-object-page.41602.html).