More info...

As for the sling, Turner Saddlery has about the best reproduction slings.  The Trapdoor and Krag 1887 sling or the Krag 1903 sling are period accurate.  If you intend on shooting in competitions as many of us do, the 1907 sling would be a better choice, and it is also period accurate.

As for the Bayonet, cleaning rods and oiler, they are usually found on sites like EBay or GunBroker.  You can always find them at gun shows too.  Here in Michigan, we have an Antique Arms Collector's show a few times a year, and you can always find these items, as well as original slings, ammo, etc. 

Hope this all helps!
Paul