There's no such thing as a holster that won't cause finish wear. They all do. Some things can be done to minimize it, but eventually you'll end up with some wear (there may be some exceptions for those guns with one of the newer, harder, ultra-wear-resistant finishes...nickel is not one of them).

Look for a leather holster with a smooth leather lining. Rough or suede linings can trap dirt that can abrade the gun's finish. Clean the holster interior frequently. Suede linings can also trap moisture, which can be bad for the gun if it's not allowed to air out and dry between wearings.

Also it should be molded specifically for your gun. If the gun is allowed to move while it's in the holster, that friction can increase wear on the gun's finish.

There are some leather treatments you can apply to the holster interior. Mitch Rosen's Leather Lightning comes to mind. You have to be careful, though, as the wrong treatment can ruin your holster, gun, or both.

Some people like to apply Renaissance Wax to their guns as a way of minimizing finish wear.

None of these approaches will eliminate finish wear, but they can help hold it off for a while.