User531388329 posted
Ended up figuring this one out.
In case someone else ever needs to build a similar query...
LogParser "SELECT date, time, c-ip, cs-uri-stem, cs(User-Agent) FROM C:\Windows\System32\LogFiles\W3SVC1\ex*.log TO Output.csv WHERE cs-uri-stem LIKE '%Username%'"
Probably crude, but it got the job done.