You say that James was a weaver. The average weaver wouldn’t have been able to afford a gravestone, so chances are he’s buried in an unmarked grave, presumably in Aghagallon COI graveyard since that’s what the records indicate.
I very much doubt there will be any graveyard plans covering that period, showing where each person is buried. Usually the grave diggers were illiterate so written records weren’t much use. Most families knew where their family plots were and could point them out to the gravedigger, but obviously if they moved away that knowledge was lost.
Have you contacted the parish to see if any graveyard lair records exist for that period? I’d be very surprised if there were, but I could be wrong.