I would like one, too.
Wait! You're looking for suggestions. 8) As far as I know, whenever people mention wanting to preserve a finish, the talk goes to two options, well, three really.
Leather supposedly wears a lot of finish slowly.
Kydex wears only certain points very quickly.
Not carrying a gun preserves its finish best.
And from what I have seen on my gun, which I carry in a passive retention leather slide holster that's pretty true. The wear on mine is very mild, but very even. Never really tried a Kydex though, so take that with a grain of salt.
Ultimately though, I don't think you physically can carry a gun in a holster for any amount of time without well, having the finish do its job. 8(