you can usually get a lawn mower air filter to work. they're at most hardware stores, especially the big ones. if it's got foam remember to soak it in 2 stroke oil. otherwise it's like a nose without snot.
please get a proper filter sooner than later. running without one is a sure way to destroy a motor. I'm rebuilding a motor that was run without one and it's a mess. i never realized there were parts of the motor that didn't have motor oil in them. the only lube they get comes from the carb and with no air filter the road dust goes straight inside with the lube and creates a mud that breaks everything down.