The War Department's "Handbook on German Military Forces" has a short section on the use of armored cars for recon that might be of some use. It came out in 1945, and was based in large part on captured German publications as well as debriefings and other information. It was reprinted by the LSU Press in 1990.

You might want to check out the modeling community as well. Some of the Osprey stuff can make a decent starting point, as they usually have decent bibliographies. Can't remember offhand if there are any mechanized recon memoirs in English or not, although I have a nagging (possibly faulty) memory of one coming out or being discussed a few years back.

You may want to put the question out on the Feldgrau forums. They should be able to help you if there's anything out there.