Jim,

Bobby Roberts' ace reference department at the Central Arkansas Library System tracked it down (it was an infernally hard term to find!). A monk bag is defined as "a small purse worn by sailors' round the neck on a cord, containing their money and valuables." From R. Turner Wilcox, The Dictionary of Costume, (New York: Charles Scribner's Sons, 1969). So I call it a good Monday when I learn something new!

Mark