I've got one Realtor sending me any manufactured homes, and expired manufactured home leads. Thats a pretty small list and rather than an automatic update its a once a month thing - if I ask.
I have had another Realtor set up multiple criteria searches which were great! One was 2-4 units, within a certain price range, in a certain number of zip codes. Another was 3/2 only at a certain price range in a certain area. I'm surprised that these Realtors haven't just sat you down and asked exactly what you're looking for.
As an agent, Searches with in a certain price range, area, type are very easy to set up. Ask you agent to narrow your search, they might not understand just what you are looking for. If that doesn't help, find a new agent!