I'm probably sticking my neck out here, but I think if you limit your vision to using some sort of 'native american print' fabric, you will be disappointed. All I have ever seen or heard of in commercial fabrics are replicas of southwest tribal patterns, most often Navaho. There is a world of native culture east of the Mississippi and in 'less famous' western areas.
If I were doing this, I would concentrate more on the design of the quilt than the design of the fabrics in it. Do some research and find some of the art typical of your father's tribe. If there is something that has great meaning to him, by all means use that. We can certainly help with art research as well if you need it.
Base your quilt pattern on a graphic design similar to that, possibly using nothing but marbles and blenders for your fabrics. Traditionally, the fibers were dyed with plant dyes as 'solids' and the beauty of the finished blanket came from the overall arrangement of different colors into a unique pattern. Treat your quilt the same way. Something to think about anyway?