the one I have in mine is the On Target trigger shield. I do have a pic of what someone on this board called a blast shield that was made out of a pie tin that is similar. I just hosted the pic for him and do not have one.
The on target one (I think) is probably a bit better. You could make one, but I don't think I would end up with one that is that straight and fit as well, plus I don't have any metal to start with (thin, but more than pie plate). The on target one is cheap enough and fits right...