There are so many reputable websites run by individual artists and traders, and family operated businesses with excellent customer service and quality authentic and handmade merchandise.
Here's a few more, and please share your referrals and recommendations with us too.
The Eastern Cherokee of NC have one of the oldest artist co-ops, founded in 1946. Fine quality, but less selection than I had anticipated. All items are crafted by Tribal members. Qualla Arts and Crafts
The Indian Arts and Crafts Act is well intentioned legislation, but can be quite confusing in the real world. It forces those of American Indian heritage and not members of federal recognized tribes to label and market their products in somewhat vague terms. This is not indicative of lower quality or craftsmanship, only the absence of an ID card.
Unless you are looking to purchase only items certified as American Indian made, the best rule of thumb is to buy what you like, what speaks to you in some way.
Native Treasures features the beading skills of one artist in Santa Rosa CA, with great prices on earrings. Some include porqupine quills and dentalium shells. Native Treasures