While I do not have a DS game system, there are several sites "freecycle.org" and "kashless.org" that offer "FREE" items from people like you and me. All you have to do is go to each site, put in the city you are from, and then sign up to the respective site.  Someone on one of those sites might have gotten a new one for Christmas and will be giving away their "old" one.

Hope one of these sites has what you are looking for (and maybe even something you didn't know you needed until you saw it posted for free)