There was a very interesting article in the Spring 2008 issue of the
Museum of the Fur Trade Quarterly, "What the Indians wanted and what they didn't want - 1843." The bulk of the article was a letter from Alfred Brunson, Indian Agent at LaPointe, Wisconsin, to Territorial Governor J.D. Doty, dated January 10, 1843. So, the items mentioned were issued as annuity payments rather than trade goods, but Mr. Brunson seemed to genuinely care about the people's needs.
Among the many other items mentioned, Brunson said, "
They want no more Sportsmans powder horns, or shot pouches, give them ox horns & they can make their own powder horns."
I don't know if this is a "trade" horn or not, but this pouch and horn set, from the Sioux, is in the Smithsonian:
This Assiniboine outfit is from the American Musem of Natural History:
There are a lot of native horns in museums, although it's hard to say which ones are trade horns, versus those obtained in raids or battles, or horns made by their owners.
Notchy Bob