Non bulky sweater/coat

So I live in New England and it's starting to get colder I have a 9 month old who is just about to grow out of her bucket car seat so I'm wondering if you guys have any ideas for Non bulky sweater and coat that will keep her warm now that I will have to take her in and out of the actual car seat and can't just wrap a blanket around her in the seat. I also have to drop Off and pick up another child at school and I have to walk to his classroom outdoors so I am just looking for ideas to keep her warm. Thank you!