What I did was purchase a K&N filter and mounted it in the stock Supra airbox. What I did before this was cut the front face off the airbox so that more air can get in from the front duct - but left the round part there which shielded it quite nicely from the engine bay.
Perhaps best to cut away only the lower half of the front face, as it will look completely stock then but give a small increase in airflow.
This mod WILL make it louder, you have been warned.