Unidentified Heraldry, Perhaps of a Patron Named Anthony or a Knight of the Order of Saint Anthony?

Beth Morrison at the Getty Museum hopes that someone can identify the heraldry that appears several times in the borders of their manuscript of the Invention et translation du corps de Saint Antoine:

Quoting from a blog-post by Bryan Keene and Rheagan Martin she writes:

On this manuscript page, a handsome knight with long hair and shiny armor kneels in perpetual prayer and veneration before Saint Anthony Abbot of Egypt, whose life and posthumous miracles are recounted and wondrously visualized in the manuscript. The patron’s enigmatic coat of arms features on several decorated pages of the rather short book, either emblazoned on a shield topped by a helmet and held by an angel (whose wings mirror the fleurdelisé pattern on the escutcheon) or held by a lion as a banner or standard. In heraldic language, the arms can be described as follows: sable, quarterly I and IV fleur-de-lis or, II and III fretty argent. These devices declare the early owner’s identity and yet have simultaneously resisted decipherment, befuddling scholars. The knight’s motto, however, can be easily read: "Du bien d’elle", a French phrase that may be translated as “Of her goodness,” perhaps referring to a bond or vow taken for a lady by a knight devoted to a chivalric order dedicated to Saint Anthony. Additionally, a puzzling phrase was penned, presumably in a 15th-century script, on the last page (folio 56v) of the manuscript: "Vive le curé de . Vincent à sont desir // P Martin [monogram] GMartin". The same hand likely also wrote "Girin martin p(ro)thono(taire)"(?).

The Getty’s webpage for the manuscript (MS. Ludwig IX 8) has more than 20 further images and a bibliography.