I am assuming you are talking about horizontal shoulder rigs. The only ones I have seen are custom jobs, I think the old Alessi Guardian was one, and I think Null made an upside down one for the bodygurad 49 type revolvers.
I am somewhat surprised to see that Galco currently lists some of their horizontal shoulder rigs for the smith bodyguards as well. I assume they use a trigger guard break. I am guessing they are probably special order, but Galco stuff is pretty decent though retail is pricey.
Personally, I would almost say it is better to buy a regular hammer revolver and a cheaper shoulder rig to go with it, always nice to have a spare gun. When I feel like carrying a j frame in a shoulder rig that is what I do, switch from a 649 to a 36.
I would not use a generic-ish nylon holster for the bodygurad, even a good one does not retain enough to keep a revolver in by the trigger guard.
