k&n air intake filter cleaner?

i have an aftermarket air intake thats similar to a k&n filter/intake system just another brand. does anyone that has one know of a home brew for the filter cleaner solution? by the time i finish a bottle of filter cleaner, i still have 3/4 bottle of the filter oil left. unfortunately they dont sell the cleaner separate of the oil, they only sell them in sets of cleaner/oil. i was wondering if anyone knows of a home recipe that i can mix myself. any idea if something like simple green or some kind of off the shelf degreaser is safe for the application?