A quick Google search on the term "flat head wood screw" yields:
    http://www.boltdepot.com/wood-screws.aspx

Here's the link to the Google search results, if you want more options:
    http://www.google.com/search?hl=en&q=flat+head+wood+screws&btnG=Search

Ross E. Schacher
Grafton, Mass.