Flow Stream producer

It seems that Streams are a great way to feed Flows. However, I’m not sure how to create a Stream that suspends while waiting for data from an external resource. For instance, I’d like to create a stream that pops items off of a redis queue. This queue may be empty sometimes while waiting for new input. Is there a way to create a stream that will do this for a Flow without creating a GenStage producer that wraps it?