Joseph Mudd's "With Porter in North Missouri":
http://www.archive.org/details/withporterinnort00mudd is available as a FREE download in various formats of your choosing...
Several other books are available at the same price...
http://www.archive.org/search.php?query=subject%3A%22Missouri%20--%20History%20Civil%20War%2C%201861-1865%22
...of course this whole URL isn't going to work so you'll have to copy and past it into your browser. You might bookmark it while you are there.