Try one of the old small gun shops. 35 Remington used to be more commonly available for the marlins out there. I don't see much in the larger stores. I usually buy brass at gun shows and reload but see a few boxes of loaded rounds at the shows as well. if you are not into casting lead bullets, there are lots of lead bullet makers of 38/357 bullets that work great in the 35 Remington with a light load. See the Lyman cast load handbook.