I have a Mossberg Maverick 88 pump. I am trying to change the the pump grip to a pistol grip. There is a nut with 2 slot in it to remove the old pump grip. I know there is a special tool to remove this nut which I don't have. Can anyone tell me if there is a tool I might have in my workshop to use or what is the tool called that I need and were can I buy one?