Thankyou @benschoenfeld, your solution works. I had something similar to this but something was wrong, after copying your answer I got the desired result similar to your original question.
I had also previously tried creating my own topic under
resources, and then referencing it in the
sns event setup. According to the documentation it should be possible to specify an
arn in the event setup, and rather than creating the topic (when you specify a
displayName), it references an existing topic, but I couldn't get that to work.
I definitely think this is worth improving, did you end up creating a ticket for this?