Galco makes an inexpensive shoulder holster that seems pretty good. Maybe they make one for your pistol.
Click on: Galco holsters; Holsters; Gun holster, pistol holsters, western holsters, shoulder holsters, leather holster and Glock holsters
Send a PM to Old Padawan (his name is Bill), here on this forum. He works for Galco, and knows all of their products.
I don't believe that you will find anything in leather that will be as inexpensive as your G.I. shoulder rig was.
However, since speed and holster-fit are not issues for you, maybe a Nylon-fabric rig would do the job at a very reasonable price. Maybe Uncle Mike's?
You could also buy a belt holster (Galco, once again, makes good soft-leather, inexpensive ones) and add G.I.-style shoulder straps to it. Any shoe-repair shop could sew them on.
I retired many years ago, so I am not current with what's available from whom.