Thanks, aanker! Your post got my mind working. The HSNA website
http://hnsa.org/doc/subreports.htm has digital copies of the
original patrol reports for most WW2 submarine patrols. Reports for
all 10 patrols of USS Balao (SS-285) are available there. This is a digital image of the original reports, digitized from a microfilm copy and printed in the original typewriter font just as it was typed by the yeoman in the Balao's office. This is as primary a source as anyone could demand. The title page of the first report reads:
U.S.S. BALAO
REPORT OF
FIRST WAR PATROL
From: 25 July 1943 - To: 13 September 1943
Since the historical Balao began its first war patrol on 25 July 1943, and was commissioned and worked up under wartime conditions, it is unlikely that it could have been available more than a few days prior to that date.