For a scoped handgun, something like the Uncle Mikes bandoleer holster, something that you can wear under a jacket to give the gun/scope some protection from the elements, and that you can access from a sitting position.

I made holsters for a lot of years, and made a holster for my scoped 10" Contender, it was modeled after the old WW11 shoulder holster. A design that I always thought was pretty useful..