I have a Davis made Minnesota S the same as in your picture that uses a "Davis long" needle which measures a little under 2". New old stock Boye 10 or MTx190 commercial needle will both work. 15x1 or Universal needle is too short to make up difference in length by cheating.
Jon
http://www.sil.si.edu/DigitalCollect...f/sil10-37.pdf
similar manual for your "S"