Coater7,
It is a straight-forward job to drill the hole in the cover oversize, then make a thin wall bush from brass, shrink it in, then drill the grease nipple hole through the side, and ream the bore of the bronze bush to size. The drilling should be done on a drill press (or mill, if available), with the cover on a jig or angle plate set up such that the original hole is at 90 degrees to the hole. You can make a mandrel out of mild steel round, to act as a guide when setting up.
Every cover I have seen, has required bushing.
Richard