I made a holster. I used an Uncle Mikes, cut the top and had a seamstress sew some material onto where the cut was made so it wouldn't fray. I suppose you could use a soldering iron to melt the cut. I got the holster for about $6 and it worked fine for a Buckmark with a 5.5" barrel and an Aimpoint scope. I got rid of the pistol but kept the holster!!!
I actually have an Uncle mikes shoulder harness that was for my beretta px4.
I cannot remember the size, but it should be easy enough to find out. Anyhoot my Ruger Mark III 22/45 with a reddot scope fits very well in it in reverse where I can snap it in securely.