Cotis, A custom maker like Bowen, Huntington or some other should be able to build you one.
I have a custom Ruger Bisley with a octagon barrel I bought second hand that is in 45LC and has a 4 5/8ths inch barrel. Even with the short barrel it is a little barrel heavy but that seems to help with the heavier loads. Chase your dream. I really like mine. I would just be careful going with a longer barrel unless they can keep it nice and trim.
Byron
