This company makes 15mm and 28mm decals. The Shoulder and Sleeve patches/insignia should work for 6mm vehicles, aircraft, etc. A 28mm shoulder patch should fit 6mm vehicles no problem !
http://5682miniatures.com/shop/ I just ordered some from pages 7-9 of the link. They have 101 and 2ID shoulder patches, 2 units I served with in my youth. So I plan on decalling some of my DRM and Exodus Wars, etc. models with those. I also ordered a sheet ofthe USCM shoulder patches from the Aliens movie too ... check out pg. 9 !