It may be the same as other windshield models of 1929 but I certainly don't have the dimensions you need.
This should be what Ford's dimensions were but there is a lack of fordor mention.
http://www.mafca.com/downloads/Servi...p250_Glass.jpg
Bert's Model A Store lists one specifically for the Fordor Briggs but there are no dimensions. If you have a frame, you can use it as a pattern to have the glass cut.