Hello...
I haven't been able to find a unit emblem for this Staffel either, but there is a well-known photo in a book which I have, that shows an in-flight shot of an He111H from 9/KG53 during the Battle of Britain (A1+BT), and it clearly has no unit emblem at all.
I suspect some Staffeln simply used the Gruppe emblem, similar to the often-seen photo of A1+AH on the Russian Front, which carries the I.Gruppe emblem behind the cockpit glazing. Then again, hopefully someone else may prove me wrong.
Regards...