sometimes gun stores will buy them of you
gun shop, ebay, gunpartscorp
Optics Planet and Leapers are two of the places that have parts or can order in parts for this type of gun. Parts can also be purchased on Amazon and sometimes on Ebay.
eBay is the best way to sell
Try EBay.
you should try ebay.
Gun parts .com
Gun Parts Corporation is the main supplier of Numrich gun parts. On eBay, one can find Numrich gun parts. On Amazon, one can find a few Numrich gun parts.
Sites such as Craigslist, eBay, or local classified is the best place to sell your gun for a low price.
Interchangeable parts for machinery
The best place to sell airsoft guns is on eBay. Believe me, everyone who wants an airsoft gun, the first place they look is eBay. Oh ya, if your selling it brand new put it on eBay express. Either way, somebody will buy it if its not too expensive or a piece of crap.
Try Numrich or Gun parts corp. If you're real lucky you might find it on Ebay or Gunbroker. Local gun shows sometimes have odd parts vendors also.
It's a collectors edition bonus. But if you really want it, people do sell the codes on eBay for about $15US.