No such thing as a 1891 Mauser..??.. Hmmmm...Your rifle must be a figment of your imagination... Along with all of those poor folks who have imaginary 1888, 1889, 1893, 1894 and 1896 Mausers.......

As far as getting a stock, I'm sure there are models available for the 91...A google search for aftermarket gunstocks would no doubt turn up something.. Do Bishop and Fajen still makes aftermarket stocks..?..