I just went to the local hardware store and bought a $2 lawnmower air filter and cut it to the size I needed, sprayed it with oil.
Just a small side note... (this never gets mentioned and I can't understand why not)
Water can and will still pass under the filter (it puddles in the bottom of the box). K&N makes a filter sealing grease. Put a bead around the bottom of the filter to seal it to the bottom of the box.
How do I know this?
