these are for automotive use idk where youd find them, the size youd want, i hate these things though, personally id go with screws of some sort, ive found fan screws work well, if the hole and the screws are the same size you wont need a tap the screws will "mate" to the metal and grab just fine, or put the plexi on the inside of the metal and the screws will mate to that just like on case fans