This chap's book on RAF POW camps seems to have a chapter on collaborators, might be worth an ask? :
Oliver Clutton-Brock : Footprints on the Sands of Time (Grub Street Publishing 2003) Oliver Clutton-Brock
Found one dodgy American cited for Dulag Luft 'Martin James Monti' as covered in a solid looking manner here on AHF:
Axis History Forum • View topic - U.S. soldiers who defected to Germany (looking for thread)