I first did it on a server then on single player both with the same results 

therefor there is no ominous shield which the Minecraft wiki denies 

how to reproduce:

1. summon a illusioner captain (illusioner cuz hes my fav illager) or a normal illager with a spawn egg
2. kill it for the banner
3.  combine the banner with the shield

sorry about the large amount of lables but trust me everything there is related