Ok so this actually ended up being fairly straightforward. The host machine is visible within the Docker container at the IP address assigned to the docker0 network interface. So all I had to do set up the reverse proxy was write the data to that IP address on port 8192 from within the container.
According to this thread, on macOS and Windows the host machine has a static hostname within the containers, but this doesn’t seem to exist on Linux hosts (peculiar).