I am in search of a flat file. One that is used for maps, or better yet, insect specimens, would be perfect. They are quite expensive, even used and so that tells me they are also hard to make.
In the meantime I am becoming one with my Xacto knife and imagery from the Biodiversity Heritage Library. If you don't know about this resource, there are thousands, even millions of archived illustrations from the 19th and early 20th century publications digitized for our use and enjoyment. They all pre-date 1923, so are exempt from copyright limitations.