I got brass stock at Ace Hardware. Drilled the hole int he middle, bent them to put pressure on the back side of the grille, used three dabs of hot glue to hold everything in place so there was no rattle.
K. I don't use a bracket on the back. I drill the hole w a 1 3/4 bit then slowly enlarge the opening w a dremmel so that tweet fits damn tight. As I'm sliding the tweet in I put a little marine silicone around the tweet lip, and that SOB ain't coming out without using explosives.
U can engineer a bracket in the back for a couple bucks. A piece of sheet metal and tin snips and done. When u get all that in, throw some caulk/silicone around the back of the tweet.