What scale are you after. There are a number of sets of national insignia and swastika's, Unit insignia is a bit harder to come by unless you get sets for specific aircraft, but there are some out there.
I build 72nd air craft and have a set of unit insignia, but it is a mixed set for bombers, fighters and ground attack. There was a set by Microscale, but like a lot of their stuff, its now hard to come by.
I am a Norfolk man and i glory in being so
On the bench: Airfix 1/72nd Harrier GR.3/Fujimi 1/72nd Ju 87D-3