I'm searching for a Marlin 39a extractor and cartridge cutoff spacer. There are at least 3 different variations depending on which year it is. The gun is a (mountie version) 1955 so it uses the OLD extractor like this: http://i11.photobucket.com/albums/a184/FastFrank4x4/oddball/Model39boltoldstyle.jpg and I'm not sure if the cartridge cutoff spacer varies for different years.
Brownell's is also in the gun parts business. Call 1-800-741-0015 for a catalog. Parts are listed in the back, including Marlin 39. It's hard to beat Brownell's for service and having the right stuff when you need it.