Link's Armorial Banner from the original comic in the instruction booklet - The Legend of Zelda 1986

 

When the shield is put on a flag, in heraldic terms this is called an armorial banner or heraldic flag.  In the Legend of Zelda the shield that Link carries varies.  In the original instruction booklet it is a red cross on gold-orange.  In the game it is a slightly yellow cross on brown.