Here are a couple of the items I have acquired for my M1.
A stock pouch that holds two clips, from olongao outfitters.
Kind of like the carbine magazine pouch. A little bit of money but they are really high quality U.S.A. made stuff. (I like the snap version better than the Velcro.)
I also bought a ported gas plug from Garand Gear. I don't shoot any hunting loads, only HXP. It still cycles just fine and puts a little less stress on the op rod.
I had Mike at Lone Star Guns do a trigger job, for $50. + shipping. It breaks just under 5lbs (like a glass rod). Way better than the way it came from the CMP.
Also put a N.M. front sight on, picked up a sling and an ammo belt.