aviator holster
I periodically carry a 4.5" Ruger B-hawk in a repro WWII "aviators holster", which places the gun slightly forward on the chest, vertically about at the breast pocket. It's not really a shoulder holster or the tanker holster from the same period.
Works for me. Keeps the gun away from the hip, no hassle with seatbelt, or clambering in and out of truck, ATV, etc. I suppose they'd work good on a horse, but I am not a cowboy. Chest and shoulder rigs seem a bit "hot" to me if the weather is warmer and one is active, but usually I am not plowing about on foot till cooler weather. In or on a conveyance, they seem to work very well.