Some contemporary information for almost any item would be from an encyclopedia, online the 1911 edition of the Encyclopedia Britannica at www.1911ency.org is a great source, a little hard to navigate but with the effort.

For those interested in Asia during and after WWI several manufacturers have figures, these include:

Cannon Fodder Miniatures - Chinese Warlord and US Navy
Honourable Lead Boiler Suit - line includes Russian Civil War figures that would be perfect for this.
Mark Copplestone Miniatures - new line Back of Beyond includes (so far) armed archaeologists, Chinese Warlords, and Russians
Pulp Figures - Chinese Gangs, US Navy, and German Seebattalion. Also a film crew and rugged heroes one of who looks very much like Roy Chapman Andrews.

One of the great books for the period includes Beasts, Men and Gods by Ferdinand Ossendowski concerning the Russian Revolution, Mongolia and contains several great scenario ideas. These scenario ideas will show up here soon. And for general background information, from the great game to the 1930s, and feel of the period almost any book by Peter Hopkirk (Foreign Devils on the Silk Road, The Great Game, Setting the East Ablaze, Trespassers on the Roof of the World, Like Hidden Fire).