Tim,
This is not primary documentation but-----:
In "Sketch Book 56, Vol. VI, Indian Allies", pp.14, by Ted Spring. He mentions that by 1756, the French and Indian War Period, French Traders were trading glass powder horns to Indian Allies of the French. Mr. Spring also mentions that "Finger Woven" cloth powder horn straps were being used.
There is all kinds of info on the net about glass powder horns, even those made at the Wistarburgh glass factory. Lots of pictures of glass powder horns also.
Randy Hedden