Foot warmers and disposable. Thermal socks and/or good winter shoe liners or winter workboots.

You can also get heaters for the truck/car http://www.harborfreight.com/12v-auto-heater-defroster-with-light-60525.html

Lacking all of those options, you may want to see a doctor about poor circulation or other, possible medical issues.

I use toe warmers inside my boots on particularly cold sessions. https://www.amazon.com/HotHands-Toe-Warmers-Odorless-Activated/dp/B0007ZF4PE

I know a few people who love their boot gloves. https://www.northerniceanddance.com/boot-gloves-lights-boot-covers-p-928.html

You might be surprised what a difference something like simple leg warmers can make.

If you can find zip off or snap off warmup pants, it’s an extra layer you can shed when you get warm or add when you get chilly. I wouldn’t wanna wear them the whole time, but they’re nice for beginning and end of the session