Remington m1871 Oviedo

I recently bought this rifle. I am trying to get the fore grip off and it has a screw that goes into a type of blind nut from the left to the right side of the grip and the stock tucks into a nose piece. It of course is frozen most likely by rust. I have tapped with a hammer on top of the slotted screw head on top of the screw driver. Bent screwdriver tips trying to turn it. Used a C clamp with a socket and screw driver tip only to break it. I am thinking I am drilling this out. I need to find some parts to replace this if at all possible. I need to get this off to make sure the barrel is not pitted or compromised under it as I want to shoot this gun. Anyone have any ideas as to where I can get the parts? I may get by with just the screw if I can salvage both ends of the blind nuts?? Thanks in advance.
Lyle