Hello again captnenglish!
The only colour illustration of Helmuth von Pannwitz that I've seen is this book cover for John R. Angolia's "On the Field of Honor: A History of the Knight's Cross Bearers - Volume 2" (1980). I've read somewhere (over at Axis History Forum maybe) that it's a portrait of von Pannwitz and it sure looks like him, Eichenlauben and all. Angolia just states that the cover illustration is "Courtesy U.S. Army (Captured War Art Collection).
"On the Fields of Honor - Volume 2"
This was the second volume of a planned seven volume series that John R. Angolia was going to write for Bender Publishing but so far only Volume 1 (1979) and Volume 2 (1980) have been published... Quite difficult and expensive to find these days but I think these books where the first ambitious books on the Ritterkreuzträger published in english back then.