WG,

You might have to do some mods yourself to a holster that is designed for the gun, sans red dot. With leather, it is pretty easy to make a cut starting at the top of the holster at the center of the red dot mount, running down the body the length of the mount. Then score 90 degress on each side the width of the mount. You can then fold these "flaps" out some to allow the gun to fit in and use the flaps to help hold things. or you can cut these flaps out creating a wide opening.

With this in mind, the Hunter brand of holster makes an easy conversion, as they are inexpensive, and not lined.

Craig