So rummaging through the documentation for outputs.conf, I found that there is an option for sending out syslog output.
where you can set the hostname field -
syslogSourceType = <string>
the excerpt from the same documentation,
Data which does not match the rules has a header, optionally a timestamp (if defined in 'timestampformat'), and a hostname added to the front of the event. This is how Splunk causes arbitrary log data to match syslog expectations.
you can try this out , hope it works.
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