Double necro!
So as this is a subject that interests me- one possible house rule for non-evil characters to get a permanent or semi-permanent Death Ward:
The Lord's Banner of Crusades (from the APG) gives a constant hollow effect much like the skull. You could allow players to attach a spell to it from the hollow list much. The price is actually 40,000gp more than darkskull (20,000 if you craft it), so I feel its cost doesn't need re-balancing.
Cheers!