I know what you mean. This may sound crazy to some but I actually have a raincoat for my bags just in case - particularly when I travel to London & Rome with worst downpours I've encountered. I don't think you need this for your DE as it should be pretty weatherproof on its own but in case it gets realllllly bad you can pull this out to protect your baby.
https://www.containerstore.com/s/cl...orage/handbag-raincoat/12d?productId=11003512
Sahhhh cuteeee! I imagine these would be perfect for Hermes Kelly's and delicate Chanel lambskins.