My gun came with the original tank crew holster, that I since cleaned and stored. I ordered one of these to use when I shoot it. They're not 100% correct, but they're pretty close and pretty good quality. Also 20% off due to Black Friday.

https://www.ww2gear.com/p-39627-us-m3-leather-shoulder-holster-for-m1911a1-45-russet-wwii-repro.aspx