Welcome Brett, I'm a bit late to this thread. I have some ties to Nebraska, as my grandfather and his brother homesteaded there in the mid 1800's. He packed up his family and moved to Wisconsin in the 1860's or so. I too have a NOID similar to yours that I'd like to ID, but have not been able to. It was given to me some years ago. It blooms quite late.
Believe it or not, this is the same flower, one picture taken in the shade,and one taken in some sunlight. The first picture is closer to it's real color then the second, exactly why it's so hard to ID them from a photo. I think your idea of purchasing a few known iris that are similar so that you can compare bloom time, hight, and color will be the best way to go to get an accurate ID.