I brought your question to the attention of our manufacturing folks.
It appears that unfortunately no one makes a long short filter that
would fit the front air intakes. They'll investigate whether a
different output screen might work better than the current one.
In an environment with a lot of coarse dust, if the back screen gets
clogged just take a vacuum cleaner to it. If the cleaner is powerful
enough you can do it without removing the grill, otherwise remove 3
screws from the grill, swing it aside, vacuum, replace.
-- Carl Rigney cdr@livingston.com