Suzuki Gt550 air filter?

Hello,
I just recently checked my air filters and they are filthy. I'm on a budget because I'm a broke stingy college student.So, I went on the interwebs and read that engine oil works well as an alternative for air filter oil. I have some crank case oil laying around and was wondering if that could work too? Also, where can I find replacement foams for my Suzuki. I can't seem to find any...

(1974 Suzuki GT550L) If any one wonders what model and year it is.
Oh, and I don't have pods, I've got the original air box.

Thanks for the help!