A field holster is by no means always a belt holster. This one, the Bianchi HuSH, is my favorite for the field not least when hunting with a scoped pistol (image cheerfully cadged from another forum, by yours truly, the holster's creator):
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The HuSH was featured in the March 1985 issue of Shooting Times, by Dick Metcalf; as a result of a hunt in Wyoming by a group of us from Bianchi. Gratifying that it still seems to be made by the company.
A flap accessory is available and enabled me to crawl in dirt and mud, rocks, etc. with a scoped Redhawk without any of that ever reaching the pistol or its sights.