Hi jabberwok,
You may want to try
www.aerospace.bombardier.com/. This is the web address of the company that now owns both Shorts and deHavilland Canada. The pic I described above is from the DH archives, photo number DHC 12672, so they may very well have some info from Shorts.
I'm sure if you contacted the Public Relations department of Bombardier and explained your quest, they'd do their best to help.