I looked for the same thing- with my Hunting vest, and rain gear etc., a side holster does not cut it, nor does a bandoleer, or cross draw.
I took an Uncle Mikes holster that fits my Raging Bull 454 with 8.5 barrell, sewed wide black webing straps with adjustable parts, at the bottom and mid section of the holster, and then a top that straps around my belt. I had this stuff from manufacturing back packs.
What resulted was a perfect holtster, that doesn't need to be strapped tight aroung your leg. Comfortably secure works fine. It's low enough so I can quik draw, sit in the truck and drive, neal, and move anyway I need to in the woods.
I can carry a rifle with this big hog leg also with this type of holster, and the weight doesn't bother me.