I too suffer from cold feet whist on the bike. I use Seal skinz socks and neoprene over shoes. Some days I still have cold toes.
I read that circulation to the extremities can be improved by including ginger in the diet. The article in a cycle mag stated ginger helps to open up the capillaries improving circulation and therefore heat transfer to the toes and fingers.
My winter pre ride drink or mid ride when carried in a thermos flask is made from a piece of ginger about the size of the a thumb from tip to first joint. Peel and cut up into v-small pieces. Put into a jug and pour in about a pint of boiling water. Leave to stand until cold.
Strain off ginger 'bits' bring to liquid to boil add fruit tea bag, when required strength achieved, remove bag and pour. Honey can be added to sweeten.
A find it a refreshing drink to carry in a flask as it doesn't 'age' as some drinks can.
It also has a warming kick when you drink it.
I can't swear to any huge improvement in foot warmth but I think it's helping. Might be all in the mind