UNI Filters sells their various grade pore filter foam in sheets.
https://unifilter.com/online-catalog/accessories/
Available thru Amazon etc...
https://www.amazon.com/s?k=uni+filte...86&ref=sr_pg_2
They do make a 8.5" X 3.25" assembly that might work for you if you split it in half. Your other post stated you were pretty limited on hood clearance.
https://unifilter.com/online-catalog...otive-filters/
https://www.kartek.com/parts/uni-fil...r-housing.html