A unisex hoodie! The cozy, snuggly feeling of a hoodie stolen from your boyfriend, no thieving required. Oversized with a high-neck hood to shield your throat. Based on menswear sizes, I recommend women order a size smaller than usual (see the size chart). 
 
I've searched high and low for a sweatshirt fabric with no spandex. Spandex helps stretchy fabrics snap back to shape, but it's also a form of plastic! This fabric manages to keep its shape just fine. It's also thick and cozy warm, and you can throw it in the washer!