Not sure if you want the photo from 1919 specifically, but Wikipedia has several photos from 1920/1921 and some unattributed dates:
Public domain
Public domain
Public domain
With Rüdiger von der Goltz(this is likely 1919)(how do you scale the pictures here?):
It says here that the photo is in public domain in US, but it’s not on Wikimedia for whatever reason, so I can’t get an English version of the text.
Uploader lists the source as this book:
https://www.amazon.co.uk/Keller-Fomin-Gagkuev-Balmasov-Ganina/dp/5858241700
on Fyodor Arturovich Keller
These guys stick their watermark to the photo above, though I have no idea whether you can do that to a photo made a 100 years ago.
https://www.sz-photo.de/?16607724099100603390&MEDIANUMBER=00295530
They also have this one: