You should be able to order Remington factory 30-40 ammo from Cabelas or a site like Cheap-As Dirt.  It is available, but most stores will not carry the cartridge anymore.  Many of us faithful Krag shooters hand-load our own ammo.  Dies, and everything else you would need are readily available.  I personally load a 165 grain Hornady spitzer with 38.8 grains of IMR 4064 with excellent results!  If you buy factory ammo, save your brass! :)  Good luck with your Krag...  it should provide you lots of great shooting!