About WW2 holsters, the model 1916 for the Colt 1911 or 1911 A1 can be easily modified to one strap mexican holster. I've done that many years ago:
[edit:links to images lost]
I just discarded the brass button, the rear hanging device, the inner wooden block and oppened the bottom as I was using a 5 1/2" . Folded the flap rearward to be used as the belt slide and opened this flap around the "US" stamp to make the "mexican" band, with some scalloping done with a small punch around this band.
A way to make a cheap holster with some surplus item (when done the surplus holsters were cheaper and less collectable than now)