You'll nee a Bisley hammer, trigger, grip frame & grips.
Power Custom & Brownell's has the parts, as posted above.
It would be cheaper to buy a Bisley, then sell your SS w/o the mag cylinder - using it in the new Bisley.
It's also cheaper to buy a Bisley, switch out the parts you need, then sell off the un-needed gun for almost what you paid for it.