After more searching, I have found what is the correct coat of arms for Walter Giffard. It is not a blue background with silver lions, but a red background with silver lions (the blue shield is a later, cadet branch of his family). His blazon may be found in several books, including the authoritative Sir Bernard Burke, "The general armory of England, Scotland, Ireland, and Wales:", copyright 1864.
Blazon: gules three lions passant in pale argent
see the image for Walter Giffard's Coat of Arms at