You may want to see if the Comtek agent covers this. There is a sample template here
but you can use NPM or SAM to build these custom pollers.
I noticed you mention Syslog specifically. Do you already have an AS400 agent like Townsend or Powertech that is converting AS400 messages to Syslog? If so, you can create rules on the Syslog Viewer utility on the SAM server