Sorry, I don't have a pattern for this. I just started with a basic ball pattern for the head and did a trial and error process working with the proportions till I liked what I saw...I know there are others out there who sell similar crafts or may have a pattern if u search around.
glad you like it! .... if you do ACTUALLY want one, there is another deviant who makes a different version of master chief crochet amigurumi doll and has a link for a site where she sells her stuff. [link]