How to use shared producer with Alpakka Kafka when using Service Discovery

I would like to create a shared producer when using service discovery.
With service discovery I can do this to create ProducerSettings:

  private val producerConfig = system.settings.config.getConfig("discovery-producer")
  val producerSettings: ProducerSettings[String, String] = ProducerSettings[String, String](producerConfig, new StringSerializer, new StringSerializer)

With that approach I can call:

val producer: Future[Producer[String, String]] = producerSettings.createKafkaProducerAsync()

How I can pass this future producer to ProducerSettings when creating a flow? e.g.