I really like my Bianchi Suppression IWB Holster. It is really comfortable and and easy on your pistol while at the same time providing retention. I am not sure if they have a railed model but, it is worth checking out
We can make you a custom one to suit your needs. Just shoot me a pm and we can discuss what you need and go from there. Possibly something like one of these but for your 1911.