Cabelas carries a hammer "extension" ($10) that comes in silver or black. I've got one of each, used on a stainless Encore rifle and a blue Encore pistol.
They call it a hammer EXPANDER, not an extension. I guess they figure an expander expands the hammer to the sides where an extender would make the hammer longer to the rear of the gun.
These are really a good safety item for guns with scopes. I accidentally fired a shot into the ground once while trying to let the stock hammer down while hunting. The gun was in front of me and close to my chest. Encore pistols are normally loud, but when one fires 12 inches from your head, it's a real blast! Deer don't like it much, either.