Just wait till your 18, hehe, It feels wierd saying that, because I used to hate it when people told me that. But seriously, Just use Ebay, or go to another airsoft fourm that doesnt have restrictions on the NAR section.
Or you could get someone you know, that is age verifyed to sell it for you (I didnt just say that)
But really, if I wanted to sell something or even buy something, i'd check Ebay before I checked any airsoft boards.
Erik