Most people are using 8-9 oz, or 9-10 oz Hermann Oak veg tanned leather for making holsters of that sort. There are other veg leathers in those same weights that will work, but Hermann Oak is the best in my opinion.
I am looking to use leather as the “body side” of a Kydex pistol holster. I have made a few Kydex holsters that are made of entirely Kydex but want to branch out into using leather with the Kydex. What would be the best leather to use for this type of application? I want a stiff but flexible type leather that will mold to the person wearing the holster inside the waistband.