I would look on Gunbroker, maybe flea markets. Good excuse to kill an afternoon at a gun show, some will be better than others obviously. The Market Hall show run by the Dallas Arms Collector Something-Or-Other had more cool older stuff for lookin' or findin' purposes. Maybe there is something similar in your area. I have to admit I neglected to see if you listed your location before starting this post.
Sometimes gun shops have a bin of old random odds and ends on the cheap. I've seen an occasional service holster in there. Long shot for something that specific, but it never hurts to look.
I opted for a cheapish Hunter holster for my 4" M28, but I'd like to find a cool flap holster for it. I'd likely have to learn how to make my own or have something custom made to get exactly what I want. Neither is an option at the moment, but it's always nice to have something to look forward to.
Good luck on your search.
