Are you using a toe or shoe cover? That'd be step one for me..
In the synthetic range there are options as well, lots of thicker poly socks, fleece socks are an option too. Covering more of your leg, like socks up to your calf, might help too.
Again, i'd make sure you're cutting wind into the shoe in the first place tho...my feet are on the cool side as well (although my hands are hot), and that's what works for me...i'll ride two two pairs of booties (really form-fitting Pearl Izumi on the shoe, and then Sugoi water proof booties overtop) for most of the winter here.