I've trolled ebay on several occasions and been successful, but it's time consuming. The seller doesn't really know what they have, so you have to cast a wide net in your search terms.
Found a pristine WRA Garand barrel.....just listed as 'old hunting rifle barrel'. Luckily he posted a pic with a mashed W logo. On another occasion found a McKeever pouch, NOS, listed as "leather ammo bag".