Here's another thought, possibly a no cost solution:

If you could scrounge up a junk hammer with a spur you like, cut it off with a hack saw. Once you get thru the .002"-.003" of case hardening, it's easy cutting.

A carbide cut off wheel in a Dremel tool works well.

With a Dremel grinding wheel you can cut a groove in the bottom of the spur the width and radius of your original 455 hammer top surface and glue it on. Almost any glue will likely hold it in place and I'd start with Wilhold glue. Worst case scenario you can resort to epoxy. The spur can always be knocked off the hammer to restore the gun to original.

__________________
Jim
S&WCA #819