There were probably about 6 different Visor manufacturers back then so you've got to research them pretty good as many were very similar in design.
Check out this guys stuff as well as my last link way back in 2009.
http://www.bigjims.net/visors.htm
The 54 & 55ist series Visor for the one piece windshield is the 4th one down the list and the mounting bracket is the last one on the list! He doesn't have a picture shown on the web site but he could get you more information?