Be careful about what foam you get for a DIY filter. Some open cell foam (the kind that passes water) is treated with fungicides to prevent mildew in outdoor applications, "EZ-Dri" does for sure. What might work well is acoustic foam. They sell it in big sheets. It's the dark gray stuff they line recording studios with to get rid of sound reflections. It has a 3D surface texture , kinda like egg crate, which would help create more surface area for your filter.
I would say find a foam dealer in your area and ask for open cell or reticulated foam. Ask to make sure it doesn'y contain fungicides or fire retardants.
I would say find a foam dealer in your area and ask for open cell or reticulated foam. Ask to make sure it doesn'y contain fungicides or fire retardants.