Fleece lined leggings! Athleta makes good ones but they can be on the spendier side. I’m sure there are plenty others that are cheaper. And also, I like grippy socks to keep my feet warm.
My follow-up question to yours is: Are you having issues with grip in the cooler temps? It seems like even with rosin spray, I can hardly grip my silks. Maybe I need to switch to powder rosin?