Mary Ellen hasn't been around very long, so you might have a hard time finding her meet outfit cheap. The ones with lots of meet outfits on eBay have been around much longer (such as Molly and Felicity). You might consider buying one of her other outfits instead since I'm pretty sure American Girl isn't selling the meet outfits separately. The only time I've seen them sell meet outfits separately was when they did the BeForever conversion maybe 4 years ago. You can certainly call them and ask (I believe "it never hurts to ask"), but in recent years they have been requiring proof that you were the original owner in order to buy replacement parts and fewer and fewer parts have been available.
You can certainly keep checking ebay, etc., since Costco is selling a Mary Ellen set right now you might get lucky that someone wanted the doll without the meet outfit. But I'd consider a Plan B of which alternate Mary Ellen outfit to get. The poodle skirt is adorable! And the strawberry outfit figures into one of the books prominently.
