Try this guy :

Larry Osborn is up and running with his Marlin gun screws now. He has most screws for the Models 1888, 1889, 1893 & 1894, and many screws for the Models 1891, 1892, 1897 and 39. He also has some firing pins and main springs available.
The best way of get a list is to email Larry at: marlingunscrewsgmail.com