How to keep warm on walks

Hi,

I have a 9-month-old kitten that I take on supervised walks from time to time. It's now very cold outside even with the sun out and she shivers from the cold. I purchased a jacket which allows her to move, but it's not preventing the cold from seeping in. It's useless as soon as we step out even as I hold her close to my body. Many other jackets out there seem like they are super easy to slip out of or look uncomfortable for a feline. Any suggestions on the best jackets out there that enable mobility while insulating as much as possible?