So what would the cost be to make and fit a left hammer based on using the right hammer as a model? Is this a practical thing or just one of those things which is totally cool but not cost effective?

I have tried waiting for a set of rough cast hammers from the trade in Great Britain. Last pair I inquired about he could not give me any estimate when he would have them. I think he was really thinking which year more than which month. Waited more than a year so far. Now I am on vulture watch looking for old hammers or old side plates with hammers on them. I hate mismatched hammers but understand why you see them so often. Some where in Great Britain there must be a box, bin or drawer full of hundreds of old hammers s stripped off decrepit hamnerguns.