Hello...
If your friend cannot find an original or reprinted manual on this pistol, a good reference work for this model as well as other Sauer model pistols is the book by Cate & Krause, Vol. II of "J.P. Sauer & Sohn". Pages 141 to approx. 200 offer detailed information on the 1930 Modell and Behorden.
Besides being a good read, there are many interesting period photos as well as photos of the internals of the pistols.
Of course, if your friend is interested in a manual, he will probably have to settle for a reprint of an original manual. I can only suggest what others have already submitted - try Ebay, Auction Arms, and Gunbroker, to name a few.
Cheers,
Gary