I've seen boxes of factory ammo in small, old gun shops. Usually dated looking boxes with a good amount of dust on them.
I think I saw some brass some years ago but haven't seen much since. Could try ordering it in at a local gun store but the US manufacturers haven't been selling much brass. Could also try posting a wanted post in the EE.
I've also read that some guys made the brass from 30-30 by turning the rim down and adding a groove of the correct size to the bottom. Of course if you don't have access to a lathe that isn't really an option.
I almost got a rifle of the same model as yours but the deal didn't go through (it was with my uncle, not here on CGN). I remember looking up data for it and ever where I looked said to just use 30-30 data for it.
If you can find .25 Remington or .32 Remington you can neck them up or down to make .30 Remington. Unfortunately .35 Remington, which is a lot easier to find, has a larger case head. 6.8 SPC uses the .30 Rem as a parent case but is much too short to be converted.
