The staples usually have little feet at the bottoms of the legs that fit into the recess made by the cape chisel. (like on Dave B stripe of copper) I don't think many had straight legs that went straight into the barrel.
I wouldn't try to drill anything, but instead do as Dave B suggests, and make a chisel that fits the original size, and try to bump up the original bit of metal. It's going to be thin and fragile, so don't try to bend it up any more than necessary.
Then make a new staple to match the original, put it in place, and gently tap down the tab with a flat punch.
John