Today, during an idle Google search, I found this article about the history of needlecases. It was written by a Barbara Miller, who appears to be an SCA member with whom I'm not acquainted. The article contains pen and ink sketches of various needlecase finds, many of which I had not heard before. The time span covered in the article runs from Ancient Egypt to the end of the 19th century, with most of the interesting examples being from the Anglo-Saxons and the Vikings. It also has what looks like a potentially useful bibliography.
The illustrations of needlecases and their provenances are very interesting and have greatly expanded my (admittedly limited) knowledge of the subject. I recommend it to my readers as a good potential jumping off place for further research.