Hi,
Might I suggest you have a look at the Luftwaffe Experten Message Board, or LEMB for short.
On that Luftwaffe message board there is a special section about captured Italian a/c that where used by the Luftwaffe.
http://www.luftwaffe-experten.org/forums/
You will have to register there aswell to make use of the board, but if you are interested in captured Italian a/c it is worth it!!!
As I am very interested in a/c that where captured and used by the Luftwaffe, I will add a list of known P.108's that where captured with there German Stammkenzeichen. I have 17 codes known in total. So take another look in the next few days in this topic.
Cheers,
Patrick aka Dutchie1980