We don't use anything, we either just design into the cake or we do a nosegay and jab it in the top. My brother LOVES wedding cake so the times he goes he cuts out a 1" diameter with a knife, removes it, eats it, then inserts the nosegay.
No one has ever said anything except a few of the people at the reception location that wonder why he is eating the cake. No one has ever complained a year later when they eat that GROSS frozen cake.
Try it, you'll find it much easier. The other containers are hard to hide.