I'd look into ebay and search for " 4" filter fan ". There are plenty of 4" vortex style blowers with soc filters for around 100 bucks or so.

I like the chicken wire idea, but I would put it at the end instead of trying to replicate all the tiny holes found on production filters. Instead maybe you can have the air come through just the end of the filter and this way it would use up all the filter space instead of the alternative as mentioned earlier. I too think that you probably wouldn't be able to get enough holes in the canister along the sides and then find that all the air is being sucking through the same way. Then again, is that really so bad? Like I said though, if you could have all the air coming through at once on the end, then the flow would be more even and you could use more of the filters surface.