Barbie Collector Twilight Saga Eclipse Jane Doll will be released on March 1, 2011. Amazon (or any of your favorite Barbie dealers) will have her available for sale then. Retail price is $24.95.
She's painted in the likes of Dakota Fanning, and I've read other bloggers who believe this doll uses the Lea facial sculpt, but I'm not a Barbie face expert. You can see photos of her on the web, including this one on the Examiner, and a full-body photo of her on the EclipseMovie.org fan site.