Is it still under warranty...give Weber a call...ray:
Call Weber CS and inquire on the cost of a "damper kit" for it. I bought one a kit for the Red Kettle I restored. $5.60 for all 3 dampers and hardware with free shipping this month. I was going to make one for mine as well until I called them! Only thing is, those new dampers have a AA date code on them....and the kettle of mine is pre 79 with no date code! That will confuse the crap out of someone someday when they look at it! :heh:
I think the best (and easiest) way would be to find a piece of sheet metal larger than your hole and just use some small screws to screw it on there.