The claim information we had came from Dr. Frank Olynyk's lists, which gave the location as "K-3860, vicinity of Lodi". When we were writing the book there was no
online map co-ordinate converter and no Google Earth. Now that reference (Square qK3860 on the North Italian Grid) can be converted to 45° 26' 10'' N, 9° 21' 57'' E, between Vigliano-Bettolino and Caleppio.
I don't know where to find the american documents you want but the USAF Historical Research Agency is a possibility.
I do not know of any surviving documents from 4.(F)/122 except the
namentliche Verlustmeldungen (personnel casualty reports) held at the Deutsche Dienststelle in Berlin. It was from there that a German researcher obtained the information on this casualty for us, about 25 years ago.