I wanted a very light walking rifle and used pre-WW2 H&R .44-.410 Garden Gun frame as platform and had John Taylor fabricate several barrels to fit, so that I can choose .32-20, .38 Special, .44-40 or .45 Colt, depending upon which revolver is going with me. Still have the .410 shotgun barrel too. With a 20-inch rifle barrel or 26" .410 gun weighs 4 and a half pounds. No pony needed.
Not least expensive option, but no other way to do it this elegantly.
I am delighted with the result.