If you want a leather holster, there are any number of custom and semi-custom makers who can help you out.
I had a heck of a time finding a plastic holster for my 3" m60 - even those that were open at the bottom to accept a longer barrel did not work, as the target front sight would not allow the gun to fit. I eventually found one with a retention mechanism that locks the trigger guard in place, and I took a saw to it, opening a groove the full length of the holster to allow room for the sight. The gun still fits snugly and the retention mechanism keeps it secure. It's not cosmetically perfect, but neither am I...