Carbine accessories:
Bayonets, 15 and 30 round magazines, carry cases, 15 and 30 round mag cases including the "stock pouch" that can fit over the stock around the butt, cleaning rod and belt case, flash hider, bolt disassembly tool, piston nut wrench, books and manuals.
Most items these days will be foreign made, often junk.
Bayonets:
The Carbine bayonet was the M5.
There are the original WWII leather handle versions (expensive), the post-Korea plastic handle versions (not so expensive) and several replicas, with the Chinese being poor quality.
Sources are ebay and Gunbroker.com for originals and replicas.
Online surplus dealers sell originals and replicas, do a online search.
Chinese replica...
Chinese M5
Sling and oiler"
Most slings are replica, many original oilers are still available.
Again, ebay and Gunbroker.com and online surplus dealers.
International Military Antiques sell replica Carbine carry cases (don't get the fleece lined one, it causes rust), and replica oilers.......
Case and oiler
Fulton Armory sell most Carbine accessories. Note that some are not "correct" Carbine accesories, as example the cleaning kit # FA-A173-C is really for the M14 Rifle.
They do sell new made 15 and 30 round mags, original bayonets and scabbards, and the book "The M1 Carbine Owners Guide" would be a great gift..
Fulton
Also:
Amherst
Bill Ricca
Gun Parts Corp