Outer Limits 4x4 Board

I did a service on the old rangie on the weekend and went to repco to get a new air filter. They didn't have a listing, but the guy told me he sold a customer a navara filter which he assured me would work. Beuty I thought, went home and it does fit, but instead of the air going through the filter it would go straight through the hole. Can anyone recomend a good/cheap spot to get an air filter
cheers