There's no simple built-in way to do so. The only control over history log size (that I've heard of) is via Enterprise Manager--right clicking on SQL Agent, selecting properties, and messing with the settings in the "Job System" tab, but as you note this is a "one size fits all" situation, and does not provide control over the history entries generated by individual jobs.
The best bet is to configure this to retain as much history from the one job you're interested in, and bear with however much more data gets loaded from all the other jobs.
If this is too cumbersome, you could devise your own routine (configured as a job and fired off perhaps daily) that went through and manually deleted the desired chaff from sysJobHistory. Tricky, but not impossible. (Basing retention on assignment of jobs to categories, rather than by the individual job names or guids themselves, suggests itself.)
Philip